So I do have a jailbroken iPod Touch 3g running iOS 4.1. Yes, the 4th generation iPod Touch has come out, but I don't have that much money to throw around. So, if you want to buy me one, I'll be happy to give you my PayPal email ^_^. On a more serious note, Apple has released iOS 4.2 quite some time ago. Why not switch? Well, more anti-jailbreak patches, less stuff from Cydia actually works, and it's worth it to have a slightly dated, fully working version.***
What was the reason for this post again? Oh yeah: Sources. Now, I don't have a huge list of sources, but you still might want to at least check them out.
SiNfuL iPhone Repo
The above are repo's that host cracked packages, meaning they have packages found in the Cydia store that you normally have to pay for but can now get for free. Between them you can get almost ANY paid package.
Hackulo hosts Installous, which allows you to get almost any (I would say ~85-90%) of paid apps on the AppStore for free, and its accessories, such as AppSync, which allows you to sync the apps you got from Installous.
BENM, while having a frighteningly little number of packages, is a dedicated source for Frash, that is, Adobe Flash Player (kind of) on your iPhone/iPod Touch. Its still (extemely) buggy, but occasionally you get something that works that otherwise wouldn't. Its definitely a project to keep track of.
***I was just too lazy to take the extra steps to jailbreak it :P