I can’t find any theme for Wordpress MU home page, except edublog home theme. But you need to do a lot of modification to use it. I got a easiest to change the home of WPMU, and not to destroy the layout of your favorite theme.
1. Choose a favorite theme, copy the index.php, and rename the reproduction to home.php. This is the new home page.
2. Delete original code between <div id=”content”> and its close tag </div> in the new home page.
3. Open home.php in the home theme which is the default home theme of WPMU, copy the codes between <div id=”content” class=”widecolumn”> and its close tag </div>. Back to the new home page, paste the code under <div id=”content”>.
4. Upload your new home page to your favorite theme folder, you got your new home in the style of your favorite theme.
This is what I do in my website, I’m new to WPMU, if I missed something, please let me know. Here is my blog: iiVee