Color Keyboard and BannerDisableI installed 2 jailbreak tweaks for my iPhone that I think would be useful for my needs.
First is called Color Keyboard. It basically just changes your default iOS keyboard to some downloadable themes. The one I'm using here is called iMatte-Black. I think it looks cooler this way.
The next one is called BannerDisable. iOS 6 (which will be released in the next few months) has this handy feature called 'Do Not Disturb' temporarily disabling the Notification Center. BannerDisable makes this available on your iOS 5 device.
Both these tweaks are available in Cydia (the App Store alternative for jailbroken iDevices).