AdBlock Plus
BluezWitch
CSSU Features Configuration http://talk.maemo.org/showthread.php?t=70427
Call forwarding
Conversations Inbox Desktop Widget
CuteTube http://talk.maemo.org/showthread.php?t=71826
Custom Operator Name Widget
Extended Call Log http://www.nokian900applications.com...or-nokia-n900/
Flashlight
Flashlight-extra
FreOffice
Healthcheck http://talk.maemo.org/showthread.php?t=45453
Hermes
Lens Cover Reminder
MaeModder http://talk.maemo.org/showthread.php?t=67989
Outcoming Call Vibro
Powatool
Rootsh
Swappolube http://talk.maemo.org/showthread.php?t=62312
Tweak Flash Plugin ( to play youtube videos in Face Book)
Tweakr
Tracker Cfg
Theme Customizer

Games: Again, this depends upon your interest
Angry Birds
BounceBounce
Flobby
Paper Toss
Hangman

... to name a few

You can also tune your battery life .. check below links

http://www.techiecorner.com/1633/how...life-for-n900/

http://www.shoutpedia.com/how-to-imp...-life-in-2027/