This weekend is all about classic silhouettes, solid foundations and exploring the fashions of the past.

Start in SoMa at the Chaiken Spring 2009 Sample Sale for up to 70 percent off women’s apparel and accessories from the San Francisco label’s current collection. Founder Julie Chaiken’s signature sense of easy-going yet quietly refined style comes through once again in the season’s subdued and versatile sheaths, twill shorts, jersey knit dresses and roomy leather carryalls.

• What: Chaiken Spring 2009 Sample Sale
• Where: 116 New Montgomery St., Ste. 820, 415-777-1895
• When: March 19-20 from 10 a.m. to 7 p.m.

Muffin tops everywhere will be shakin’ in their waistbands when they hear Yummie Tummie creator Heather Thompson is in town. The celebrity stylist who’s worked with J. Lo and Beyonce, among others, shows off her easy-on-the-eyes line of women’s shapewear, tank tops and layering pieces during an afternoon appearance at Neiman Marcus. As part of the store’s Hip Events series, the meet-and-greet offers an added bonus for big spenders. Customers who purchase $500 or more in the contemporary department during the event will receive a complimentary goodie bag.

• What: Heather Thompson of Yummie Tummie at Neiman Marcus
• Where: Neiman Marcus, Intimates and Contemporary Department, 150 Stockton St., 415-362-4777
• When: March 20 from 1 p.m. to 4 p.m.

Indulge your inner Rachel Zoe at the semi-annual Vintage Fashion Expo, where some 85 dealers will gather with apparel, accessories and textiles hailing from as far back as 1850 through 1980. Items on offer range from affordable costume baubles and bell bottom jeans to collectible Bakelite jewelry, retro swimsuits and collectible apparel from such famed designers as Elsa Schiaparelli, Chanel and Lanvin. Admission is $10 and $20 during Saturday’s early buying hours. Save $2 on the admission with this online coupon. Students are admitted free of charge on Sunday with valid student identification.

• What: Vintage Fashion Expo
• Where: Concourse Exhibition Center, 635 8th St., 415-490-5800
• When: March 21 from 9:30 a.m. to 6 p.m. and March 22 from 11 a.m. to 5 p.m.