(SHOWCASE!) This week's Bumbershoot-for-performance-nerds features two remarkable frocks: Marya Sea Kaminski of WET will perform her solo show about love and longing in an enormous dress that does tricks, and Alex Martin, from BetterBiscuitDance, will perform in the same brown dress she has been wearing since July 7, 2005. (Yes, she washes it.) (On the Boards, 100 W Roy St, 217-9888. Fri at 8 pm, Sat–Sun at 5 and 8 pm, $14. See www.ontheboards.org for full schedule.)