Some great BlackBerry apps are listed below:
Beyond411 is the fastest way to look up business listings, driving directions, and web pages on your Blackberry. It can even search based on your exact location using GPS.
Google Maps provides you step-by-step directions using GPS.
ÜberTwitter is a Twitter client that has many fantastic features.
IM+: All-in-One Messenger
Chat within MSN®, Yahoo!®, Google Talk™, AIM®, MySpace™, Jabber, ICQ®, Facebook®, Skype™ and Twitter
WebMessenger Message Alerts
WebMessenger Message Alerts puts you back in control of managing communications on your mobile device by providing powerful rules and filters for your mobile email and SMS Messages!
A full-featured telnet/ssh client for your mobile device.