And unless neopwn pulls out some magic from a hat, packet injection is unsuccessful on the n900 currently. So you would not be able to 'crack' some wep, or send de'auth packets for wap.
You could listen to open networks.
(I don't own n900 yet, will 2mrw, but I read these forums enough to know)

If you wanted to learn, google 'backtrack', then google 'backtrack tutorials - getting started', then spend time on their beginner forums, then read up on the flaws of WEP, aka why is it possible.
DO NOT WEP CRACK YOUR NEIGHBOURS!!!