• Barneys kicks off its annual warehouse sale, offering 50 to 75 percent off designer clothing, shoes, and accessories for men and women. Through 9/7. 255 W. 17th St., nr. Seventh Ave. (212-450-8400); Th, 8/20–F, 8/21 (8–9); M–F (10–9), S–Su (10–7); M, 9/7 (10–7).
• Fifteen independent boutiques from London pop up on the Lower East Side for the Wish You Were Here shopping event, including Beyond the Valley, Twenty8Twelve, Unconditional, and more. Through 9/13. 186 Orchard St., nr. Stanton.; noon–8.
• Gap is celebrating its 40th anniversary by hosting a nationwide acoustic concert tomorrow night. More than 700 musicians from across the country will participate at every Gap store nationwide. Marc Broussard will be performing at the Fifth Avenue location (nr. 53rd) and Cassidy will be at the Broadway location (at 42nd). 680 Fifth Ave., nr. 53rd St. (212-977-7023); 1466 Broadway, at 42nd St. (212-382-4500); 7–9.
• Dresses are $70, pants and tops are $30, and sweaters are $20 at the Saja sample sale. Through 8/23. 250 Elizabeth St., nr. Houston St. (212-226-7570); Th–Su (10–7).
• Everything in the store is 30 to 50 percent off at La Sirena's end-of-summer sale. Embroidered blouses are $25 (originally $40), dresses are $36 (originally $60), and beach and market bags are $25 (originally $50). Through 8/24. 27 E. 3rd St., nr. Bowery (212-780-9113); Th–M (noon–7).
• All merchandise is 20 percent off at the Eryn brinié fall presale. RSVP to firstname.lastname@example.org. 501 Broadway, nr. Spring St. (212-308-6134); W–Th (7–9:30).
• Women's shoes and handbags are up to 75 percent off at the Sergio Rossi sample sale. 160 Varick St., nr. Vandam St., second fl.; M–Th (10–6).
• All merchandise is 85 percent off at the Rachel Roy sample sale. 1411 Broadway, nr. 39th St., 37th fl.; W–Th (10–7).
• Wedding gowns from brands like Angel Sanchez, Matthew Christopher, Carmela Sutera, and more are up to 70 percent off at the Gabriella New York sample sale. Also find deals on veils, headpieces, and bridesmaid dresses from Bella Bridesmaid. 400 W. 14th St., at Ninth Ave., second fl. (212-206-1915); Th–F (noon–7).
• Three pairs of flip-flops are $20 at the Havaianas sample sale. Through 9/17. Spring St., at Wooster St.; 11–6.