Below is a list of useful cydia apps/tweets which I use.
This tweak automatically switch on/off your 3G network when you lock your device so conserve battery when you are not actually using it.
This tweaks creates a possibility of maximum 5 icons on the dock.
This allows you to view/run flash content on your Mobile Safari. Check out my previous post for more details how to get it
This shows a list of toggles where you can easily toggle the different preferences switches without running the Settings App. You can even do it while inside an app (for example, changing the brightness while you are inside an IM app to conserve power)
This make your iPhone into a VNC server so that you can remote access it through a VNC viewer.