I just recently bought a Nokia N800 (yeah i know im very late) and im having problems installing almost every application. I tried to get Mytube, it worked fine but then when i turned the tablet off and back on it wouldnt even open the app. Fring wont download either. Also it seems there is not alot of games. If someone can help me one I would be very grateful. All i have that works on my tablet is a voice recorder and the camera app.

Flash the latest diablo (unless you already have it), install the community ssu (here: http://talk.maemo.org/showthread.php?t=30648), enable the extras repository in the applications manager and install extra programs from there.
Good luck.