People jailbreak their iPhone because of Cydia and this is not been made without the repositories made by some developers. These repositories made your Cydia experience more better and some examples of this are the following:
One of the jailbreakers Cydia repositories. This is known for its themes that are hosted by Cydia and has additional stuffs for jailbreak.
Ryan Petrich’s repo
This is best for people who wanted a fresh and useful tweaks.
Filippo Biga Beta Repo
Just like Ryan Petrich’s he also develops some great tweaks which he hosted on his own beta repo.