All the neighborhood is a stage in Petworth this weekend. More than 100 hosts open their porches, stoops and front lawns to almost 300 musical acts between 2 and 6 p.m. Some you might have heard of, such as the jazz-punk fusion of the Messthetics, the lush pop of Ari Voxx or the groovy synth-pop of Wrizzards. Many of them you have not. But that’s missing the point of this massive festival, which stretches almost two miles from north to south but still feels like a block party. The main stage, which hosts music from 5 to 8 p.m. at the Petworth Recreation Center, is a handy starting point, but the best part is meeting up with friends and following your ears through the streets, where you’ll hear jazz, hip-hop duos, bluegrass pickers, mariachis, DJs spinning house and dad bands knocking out classic rock covers. If one address is too crowded or you lose interest, there’s another show around the corner (or sometimes just a few houses away). Bring a hat, because you’ll spend a lot of time standing on the sidewalk, and pack food and drinks. 2 to 8 p.m. Free.

When most folks talk about museum hopping in D.C., they’re referring to visiting multiple Smithsonians on the Mall, or maybe browsing the galleries and historic houses near Dupont Circle. There’s a much more ambitious schedule at the second Do the Loop day, which brings together seven institutions west of Rock Creek, including the Kreeger Museum in Foxhall, American University Museum at the Katzen Arts Center in Tenleytown and Dumbarton Oaks in Georgetown. (The Jackson Art Center, Addison/Ripley Fine Art, Georgetown University Art Galleries and Klagsbrun Studios, which are also participating, are clustered near one another in Georgetown.) Each location offers something different: tours of Dumbarton’s gardens and museum; sculpture garden tours and food trucks at the Kreeger; guided gallery tours with journalist and artist Bob Schieffer at Katzen. Scavenger hunts and hands-on activities for children are offered throughout the day. 10 a.m. to 6 p.m., though individual location hours vary. Free.

Carousel Day at Glen Echo Park

Saturday is an exciting day for children of all ages: Glen Echo Park’s 103-year-old Dentzel Carousel opens for yet another season. Riders can claim their favorite animal — a galloping ostrich, bounding hare, majestic lion — while the gorgeously restored carousel spins to the waltzing tunes of a 1926 Wurlitzer band organ. Each trip is $2, making a $5 unlimited day pass a great deal. But there’s more to do than go up and down, around and around: The day’s activities include free music and dance performances, hands-on crafts, dance classes, and open art studios. (Some events in the park that day, such as performances of “Alice in Wonderland” at the Puppet Co., charge a fee.) 11 a.m. to 4 p.m. Free admission; carousel rides $2 each or $5 for an all-day pass.

Project Glow at the RFK Festival Grounds

The third annual Project Glow turns the grounds around the abandoned RFK Stadium into an EDM wonderland. Performances from Chicago house legend Derrick Carter, dance-pop hitmaker Zedd, and creative back-to-back pairings like upstart Acraze and genre-hopper Wax Motif should keep the rave going, as will sets by DMV favorites including Baronhawk Poitier, Mathias, Thablackgod and others. Let’s hope the weather prevents DJs from shaking the windows of residents miles away. Saturday and Sunday from 1 to 11 p.m. $109-$279.

Independent Bookstore Day

The American Booksellers Association is celebrating its 11th Independent Bookstore Day, which means discounts, parties and more for D.C.-area book fans. Kramers in Dupont Circle has two promotions: Find a golden ticket hidden in the store for a 20 percent discount, or get a free “blind date with a book” for every $75 spent (8 a.m. to 10 p.m. Free). East City Bookshop on Capitol Hill (which is also celebrating its eighth anniversary) is offering 10, 20 and 30 percent discounts at random throughout the day, plus chances to win a curated tote of advanced reader copies or a year of free audiobooks (10 a.m. to 7 p.m. Free). If choosing only one store to spend your Independent Bookstore Day perusing is just too much pressure, consider joining the D.C. Bookstore Crawl, where hitting five out of 19 locations will get you a prize — or hit all 19 to enter a raffle for a grand prize. Stops include Big Planet Comics, Lost City Books, Politics and Prose, and the Potter’s House (10 a.m. Saturday to 8 p.m. Sunday. Free).

D.C. Cocktail Festival at Union Market

Bartenders from popular D.C. bars and restaurants like Compass Rose, Bar Chinois, the Doyle and the Wells come together to pour drinks at the D.C. Cocktail Festival, held at Union Market’s event space Dock 5. Tickets offer the chance to taste samples of all 15 cocktails, so pace yourself accordingly. This day-drinking event is divided into two sessions: The first begins at noon for VIP ticket holders and 1 p.m. for general admission, with the party ending at 3 p.m. The second session begins at 3:30 p.m. for VIP and 4 p.m. for general admission, and ends at 6:30. Noon to 6:30 p.m. $39-$59.

Plant sale at the National Arboretum

Find the perfect perennial or just pick up pots and planters at the annual plant sale hosted by the Friends of the National Arboretum. Because this is the National Arboretum, the selection can be more impressive than at other garden events around town. (Check out the website for the exact list of flowers, shrubs, succulents, conifers and other plants available for purchase.) But there’s more to do than stock up your yard: Take a class on the role of raised beds in urban gardens; visit the ARTboretum for family activities, such as face painting and games; and browse the vendor village tables, full of garden supplies, fine art, clothing and jewelry from local makers. Food trucks and local companies are on hand with refreshments. The plant sale tent is members-only until 11 a.m., but other activities are open to the public during that time. 9 a.m. to 4 p.m. Free; pay-what-you-can for the gardening class.

Maryland Day at the University of Maryland

Throughout the Free State, March 25 is celebrated as Maryland Day, which commemorates the arrival of English colonists in 1634. But in College Park, Maryland Day is something else: a celebration of the state’s flagship university, when the campus opens its doors to the surrounding community, alumni or not. There are more than 400 activities taking place, from the football team’s spring game to an insect petting zoo. (“Imagine tarantulas, exotic insects, scorpions, bees and millipedes longer than your hand for you to look at and touch.”) Try making 3D art, conduct surgery with robots, listen to musical performances, explore rare books or sample ice cream from the Maryland Dairy. 10 a.m. to 4 p.m. Free.

Reopening of the Metropolitan Beer Trail

The ever-popular bar-and-brewery crawl along the Metropolitan Branch Trail officially reopens for business this weekend. Visit 11 stops, including breweries Lost Generation, Red Bear and Right Proper, or beer gardens, such as Metrobar and Wunder Garten, to earn points that can be redeemed for T-shirts, baseball caps and other prizes. (The person who checks in the most times by the end of December wins a $25 gift card for each of the participating businesses.) The trail is just over two miles long, but you don’t have to complete it in one day. Through Dec. 31. Hours vary. Free to participate.

‘The Lord of the Rings’ at the National Building Museum

The National Building Museum’s “Great Movies in the Great Hall” is like bringing your favorite summer movie series indoors. Bring a blanket or lawn chairs, complete with a picnic, to spread out on the carpet in one of the city’s most impressive indoor spaces, among the soaring Corinthian columns. Before “The Lord of the Rings: The Fellowship of the Ring” screens, J.R.R. Tolkien researcher Joey Wilson-Brooke presents a virtual program about the role of architecture and design in the books and on-screen. Costumes are encouraged. Popcorn and beverages are available for purchase. (No outside alcohol is allowed.) Doors at 6:30 p.m. $5-$15; free for children younger than 12.

STAR Fest at Martin Luther King Jr. Memorial Library

The STAR Fest — that stands for “Sing, Talk and Read” — is an in-person offshoot of D.C.’s Books From Birth program. Bring little ones for a day of story times, soft play activities, musical performances by children’s entertainers and an area that lets children imagine their own stories. This event is designed for children younger than 5. 10 a.m. to 1 p.m. Free.

Cultural Arts Festival at Creative Suitland

Poets, musicians, dance companies and theater are all featured at this afternoon festival, including Prince George’s County Poet Laureate Khadijah Ali-Coleman. A vendor market spotlights local designers of jewelry, soaps and home decor, as well as food trucks. 2 to 7 p.m. Free.

Purcellville Music and Arts Festival

Multiple stages of music, dance and entertainment are featured at the Purcellville Music and Arts Festival, set in the historic downtown area. Attractions include a show with more than 30 artists in the Bush Tabernacle Skating Rink, a market with local makers and food vendors, and family activities such as T-shirt painting and glitter tattoos. Justin Trawick and the Common Good and the Rowdy Ace Band are among the performers in Fireman’s Field Park. Dogs, lawn chairs and tents are welcome. Noon to 7 p.m. Free.

Broadway Rave at 9:30 Club

Move over, Taylor Swift-themed dance nights, because there’s a new and very niche singalong party in town. Broadway Rave advertises itself as a “traveling dance party for adult theater kids,” with musical standards on the playlist and surprise guest appearances from the stars of Broadway shows. The D.C. edition is landing at 9:30 Club, and you’re encouraged to show up dressed as your favorite Broadway character. We’re guessing the costumes will be truly extra. 10 p.m. $20.

D.C. Chocolate Festival at the French Embassy

Returning for a seventh year, this festival is a celebration of all things chocolate — education, confection and, of course, sampling. Taste and shop in the main exhibit or check out classes and workshops throughout the day on topics like chocolate and beverage pairings and the chocolate economy. There are also non-chocolate foods and beverages in case your sweet tooth falls out. 10:30 a.m. to 2 p.m. or 2 to 5:30 p.m. $25; free for children under 12.