Jailbreaking doesnt always work and leaves your iPod vulnerable to more viruses and OS glitches+bugs. And you can get free things DEPENDING ON WHAT REPOSITORIES(sources) YOU ADD. Each offer different things and such, the basic sources do not offer many free apps from the app store. Also not everything is free, I have came across a number of Cydia apps that are not free and require a purchase. I'd say, though 90% of the apps are free. I'd also add, 70% of them are pointless, and cheap rip offs. Also, since JB hackers can't always keep up-to-date with Apple, some apps might not be supported on your device or the OS you are running. If you want more sources (repositories) google for them. JB is kind of advanced...if you want a full experience.
Here's a pretty good site to check stuff out on:
http://blog.iphone-dev.org/