Absinthe for iOS 5+. Make sure all your ipod/iphone data is on your computer (apps,music,videos etc). Then go to settings-general-reset-erase all content (this makes the jailbreak process a hell of a lot faster). Absinthe will give you instructions on what to do after.
IF ANYONE MAKES YOU PAY FOR A JAILBREAK DON'T IT'S A HUGE RIPOFF AND THERE ARE PLENTY OF OTHER OPTIONS!! If you get Cydia here is a few sources to start installing packages just go to Manage-Sources-Edit-Add-Then input one of these links.
http://cydia.xsellize.com/
http://www.sinfuliphonerepo.com/ (awesome for cracked cydia apps such as iFile and Display recorder. It also has the infamous iAP cracker but I highly suggest you don't download that).
http://ihacksrepo.com/ (if you are in to hacking games)