I have released the newest version of the WP Activate Users Plugin. It now supports Network (formerly MU) installations of WordPress. you can download it here: http://buddypress.org/community/groups/wp-activate-users/
NOTE: There is currently a bug in a Buddypress MU Installs. It works fine in NON-MU installs of Buddpyress.
This plugin is for BuddyPress and BuddyPress MU Installs and allows you to manually activate users who have not activated their account via the email link. This can be used if the email doesn’t get to the user for any reason…ie spam filtering, email host etc. It places a menu in the Users menu in the wp-admin area of your site.