MeeGo test images are now available for the N900 - see here for details. Weekly code-drops are planned for the future that will include closed binaries - right now many applications are just place holders.

Testing MeeGo on N900 is quite simple - copy the uncompressed RAW filesystem image to a 2GB+ microSD card using dd on Linux, then copy (NOT flash) a temporary kernel to the N900 using Flasher in order to boot MeeGo from the microSD card.

Reboot the N900 to get back to Maemo5.

Install instructions here.