I also use limewire for the stuff you can't find on i-tunes. Your i-pod will play most Mp3's and also if oyu have the CD it will convert it to a playlist in i-tunes at the touch of a button.
I like to use bearshare lite as opposed to limewire. It seems to give better search results and doesnt use as much of the system resources as limewire. And I've never had anything near to a virus off it, so I easily recommend it.