Can't advise on sources but I would suggest getting sbsettings( toggles) bitesms (3rd party SMS app that blows the native messaging app away) my3g( tricks your phone into believing it's on wifi, so you can FaceTime just about anywhere) winter board for themes. these are some good ones.
The sources which came already install in cydia by default is all you will ever need. Just tap in the search bar in cydia the name of the app you want and you will find it. Some apps/tweaks are free, and some are paid.