This may be of use to some WordPress MU adminstrators out there who have users who decide to move to either another blog host, or to their own WordPress install and would like their traffic redirected to their new blog for a period of time.
The redirectr theme allows the user to set this up themselves by simply activating the theme and setting up the theme options.
It may remove the need for administrators to edit htaccess files for users, or offer a new "facility" for those hosts that currently don't offer redirection.
More details and the download page is here:
http://blog.clearskys.net/themes/redirectr-theme/