I managed to free up some internal space by moving Maps, Voice Search, Google Search, and YouTube to the SD Card.
(Only works with those apps which re-downloadable from the market)
First, you MUST have a rooted phone.
Install Move2SD Enabler with External enabled and a file explorer with similar functionality to Root Explorer (ability to r/w system folders).
I personally use Root Explorer.
Not required, but I also use App 2 SD (the app). I find it very handy and a better overview of moveable apps than the built-in app manager.
Go into the /system/app folder and delete the apk's.
Also go into the /data/app folder and delete the update apk's
Reboot into recovery and wipe the dalvik-cache.
Reboot the phone.
Go into the Market and redownload the removed apps.
They should now be installed on your SD card freeing up a little bit more internal space on your phone.