• Donate your old bridesmaid dresses to Operation PROM, an organization that provides free prom dresses to girls in need. The first 100 people to donate will receive a free Revlon lipstick and nail polish. Through 3/13. 57 Grand, 250 W. 39th St., nr. Seventh Ave., Ste. 804 (212-302-1604); 11–7.
• Shop discounted designer wares at the Tribeca Housing Works spring-preview sale. All proceeds benefit homeless and low-income New Yorkers living with HIV/AIDS. Housing Works Tribeca, 119 Chambers St., nr. Church St. (212732-0584); 5–8.
• Receive up to 80 percent off Carol Kauffmann jewelry, Pamella Roland eveningwear, MCM handbags, Cassin furs, and more at the Flatotel sample sale. Through 3/11. 135 W. 52nd St., nr. Sixth Ave., fifth fl. (212-920-1211); T–Th (10–6).
• Rings, necklaces, bracelets, and earrings are 15 percent off at Bittersweets. Through 3/19. 37 Broadway, nr. Wythe Ave., Williamsburg, Brooklyn (718-218-8595); daily, 3–8.
• Slim and skinny jeans are 25 percent off in-store and online at Ann Taylor Loft. Various hours and locations.