Learn everything about herbs at Herbstalk. In its second year, after attracting some 1,500 in its first go, Herbstalk: Herbal Education for Urban Communities has grown to two days of classes, music, food and a vendor marketplace. Classes range from a “plant walk” and “Meet the Weeds” to advice on how to use herbs in oils, aromatherapy and as sleep aids or even First Aid. (There are also classes on such things as “Men’s Reproductive Health: Vitality Instead of Viagra,” “So You Want to Start a Free Clinic?” and “Herbal Dental Care.”) If you believe in the power of herbs or want to explore it – or if you just want access to the nearly 40 vendors participating, tickets start at $5 (for one-day passes to community classes, plant walks, activities for kids and the marketplace) and go as high as $40 for specific, intensive interests. Children 12 and under get in free. The event runs from 9 a.m. into the evening Saturday and Sunday at The Center for Arts at the Armory, 191 Highland Ave., Somerville.

Eat for free to welcome the brand-new Just Crust. Just Crust, the Harvard Square eatery where social justice is delicious, has a grand opening event with special guest U.S. Sen. Elizabeth Warren and even some free slices (but you have to RSVP). The shop was an Upper Crust Pizza location until the sketchy chain went bankrupt last year, and now the site is part-owned by some of the workers that filed a labor lawsuit against Upper Crust, as well as Shannon Liss-Riordan, the attorney who represented them, and husband Kevin Liss-Riordan. The event is from 2 to 4 p.m. Saturday at the shop, 49B Brattle St., Harvard Square, although the shop itself is open from morning to night.

Get a first glimpse at a new play. Lenin, author James Joyce and the founder of the Dada art movement, Tristan Tzara, happened to be in Zurich at the same time during World War I, a confluence to which playwright Tom Stopped applied his imagination in 1974 in the amazing “Travesties.” But this may be even more amazing: Joyce, Marcel Proust, Igor Stravinsky, Pablo Picasso and Russian dance impresario Sergei Diaghilev were all at the same dinner party May 18, 1922, at Paris’ Majestic Hotel – and playwright Debbie Wiess has imagined what happened in a one-act play called “Proust and Joyce at The Majestic” that gets a read-through this weekend. It’s free to attend, courtesy of Somerville’s MotherDaughter Productions, at 2 p.m. Saturday at the Somerville Community Access Television studios, 90 Union Square, Somerville. Audience members are asked to arrive 15 minutes early.

Dance, dance, dance! Watch and learn. This weekend brings the fifth José Mateo’s Dance for World Community Festival, taking place over two days and expecting attendance by more than 20,000 people. It includes the free Festival on the Common (from 11 to 6 p.m. Saturday on the Cambridge Common, near Harvard Square), encompassing four outdoor stages with performances by more than 75 local dance troupes in a variety of dance forms, including African, ballet, folk, hip-hop, Irish step, modern and salsa. The event includes festive foods, picnicking and children’s activities. A Dance Party Benefit (from 8 to 11 p.m. Saturday at the José Mateo Ballet Theatre, 400 Harvard St.) follows to support Dance for World Community outreach programs. DJ Kev D spins, and surprise performances are promised. Tickets are $30 (including food and two drinks) or $100 for VIP seating (including a table, food, two drinks and a $70 tax-deductible donation).

The festival also includes Dance Discovery (from 2 to 7 p.m. Sunday at the theater) with a free introduction to learning all forms of dance (starting with ballet, belly dance, folk and salsa) for children and adults; and a free Talk About Dance (from 5:50 to 7:30 p.m.), with discussions and world café-style conversations about dance and social change.

For information, call (617) 354-7467.

What? Not enough dancing? Have more. There’s even more dance this weekend, with free folk dancing that comes with basic instruction to get newcomers moving to the live music. (People are also invited to simply enjoy listening.) The first of these weather-permitting events features Balkan dancing with music by CoW, or Coalition of the Willing, from 2 to 4 p.m. Sunday at Forbes Plaza in front of the Holyoke Center, 75 Mount Auburn St., Harvard Square. The other dates in the series, brought to you by the Folk Arts Center of New England, run from 8 to 10 p.m. Saturdays: Aug. 3, Aug. 24 and Sept. 7.