Shania Twain [ tickets ] and Alanis Morissette [ tickets ] have joined about three dozen acts to donate items for an online fundraising auction benefiting the Rape, Abuse & Incest National Network's (RAINN).

Yahoo! is hosting the auction on its Auctions site through June 26.

Among items up for bid are an autographed guitar from matchbox twenty, three autographed hats from Kid Rock [ tickets ] and a baby grand piano from Tori Amos [ tickets ], who helped to form RAINN in 1994.

RAINN operates a national, toll-free hotline--(800) 656-HOPE--for victims of sexual assault.