Gertie's New Blog for Better Sewing about what undergarments to wear under vintage and repro clothing. Check it out here. Be sure to follow the link to Couture Allure's article about foundation garments in the discussion, which includes pictures of four vintage looks and the undergarments (like the one on the left) needed to create the correct silhouettes to pull them off.
UPDATE: One of the comments on the discussion from Brabarella includes a link to a 4 part article she wrote for women who want to start wearing foundation garments but don't know where to start. Keen!