BuddyPress.org

Take an activation URL in the activation email (send yourself a fake one if you don’t have one lieing around). Then, go into something like phpmyadmin. Look at the table for users (it’s different if you’re using WP vs. WPMU) and find the activation key. Replace the key in the URL and now you can use that URL to activate the account.

I’ve also heard rumor that someone might be working on a plugin to deal with this type of situation.