Transferring purchases: http://support.apple.com/kb/HT1848
To transfer music that you did not buy from iTunes from the iPod to a computer is contrary to its design, like trying to use the wrong end of a funnel. The right way to recover the content from a damaged, lost, or stolen computer is to restore from a backup that was not damaged, lost, or stolen.
If you've been "driving without a spare" all is not lost, but you will need the assistance of third party utilities to extract music from your iPod. You will need to spend some money. See wjosten's procedure here:
https://discussions.apple.com/docs/DOC-3141