Some good jailbreak apps for your device. You can get them at Cydia anytime.
Maps the cell towers you are connected to and displays detailed cellular information from the baseband.
Infinifolders lets you add as many icons as you want to each folder, breaking the 12-app limit, and access them trough a flick up and down.
Records directly to high quality AVI, Web interface to manage recordings, On-device YouTube uploading, Adjustable framerate and quality settings, Hardware accelerated video encoding, Activator integration for quick access, Remote control via web interface.
Now with FaceTime on 3G support. Allows you to trick applications into thinking they are on 3G even though they are on WiFi and by this remove restrictions like not being able to use VoIP apps like Skype or watch TV with slingplayer on 3G.
iBlacklist is the best firewall for calls, SMS and MMS available for the iPhone. It ables you to select from who you want to receive calls and hide messages.