Are you talking about leaving revleft.com itself or the Hoxhaist subforum? There is no procedure for simply quitting the board, but to quit the Hoxhaist subforum, click on User CP, look on the left for "RevLeft Groups" and hit it.
You'll see a listing of groups with links that say "Leave group". Hit the links for the groups you want to leave.
Shame to see you go, BTW.
