Currently I have my .htaccess file set up to redirect subdomains as follows:

http://foobar.domain.com redirects to
http://domain.com/index.php?title=foobar&useskin=bluwiki_skin

These are the rules to accomplish that:
Code:
RewriteCond %{HTTP_HOST} ^([^.]+)\.bluwiki\.com
RewriteRule (.*) /index.php?title=%1&useskin=bluwiki_skin [L]


I would like to change it to the following:
http://foobar.domain.com/test redirects to
http://domain.com/index.php?title=foobar:test&useskin=bluwiki_skin

I don't know how much you know about mod rewrite or htaccess files,
but here is a htaccess generator that has lots of options.

http://cooletips.de/htaccess/

You might also consider a php 301 redirect. This method does not
require you to change your htaccess file. You simply replace the
existing page (usually by renaming it so you retain the original) with
a simple php file. The php file is given the same name as the page you
want to redirect, the original that you just renamed. A 301 redirect
file is as simple as this:

<?php
header( 'Location: http://www.yoursite.com/new_page.html' ) ;
?>

Just replace the address to the page you want to redirect to.

More info 301 redirects can be found lots of places on the web. If you
have questions I would suggest going to an SEO (search engine
optimization) forum to investigate. These forums offer a wealth of
information on a wide variety of issues that will help you make your
site more visible.

This is what you want after the RewriteCond:

RewriteRule ^(.*)$ http://domain.com/index.php?title=%1:$1&useskin=bluwiki_skin