News4Neighbors report from last year.
Worldwide home page
Info about the Portland ride for this year
Info about the dance party thing
Disjecta page about it (location of party)
I don't know that I am so brave as to ride around Portland naked, but I am brave enough to go to a party, and ride around Portland with clothes on in a group of naked people to help support their cause. The rule is it's as bare as you dare.