I would suggest just grabbing the individual files that you want.
If you really want to grab all my random themes you can do a checkout to your HOME library. Like so:
That will create the textmate and themes folders if they doesn't exist and grab the latest of every theme I have. Most of them are too ugly for most humans ;)
Then to grab the latest version later, you can do this:
svn up ~/Library/Application\ Support/textmate/themes
Assuming you have subversion installed, of course.
I would suggest NOT grabbing everything else unless you know you want it.
I'll be migrating the most important stuff into the official TextMate bundles soon.