This is the most reliable list of Cydia repos that has almost all the apps and tweaks you would ever want on your iPhone.
Before we could get into the list, let me just explain you what is Cydia, What is a repo and such things, so that you’d have a better understanding of the products.[alert_box type="Info"]Note: Installing Cydia (Jailbreaking) on your device will void your warranty. Please do this after understanding the risks fully.[/alert_box]
What is Cydia?
Cydia is a piece of software that runs on Jailbroken iPhones. It enables the user to install custom software packages from various sources (repos/repositories) into your iDevice.
What is a repo?
[On an iDevice prespective] A repo is a hosted space into which a developer uploads custom APTs that can be loaded into your iDevice.
What are some of the must-have repos on Cydia?
Here goes the list:
What are some of the best Applications for my iDevice?
I’ve worked on a list of applications that would best suite you. Take a look at Top 10 must have Free Cydia apps for iPhone/iPad 
Now that you’ve had a glance at the repos above, for the newbies, here are some tutorials: