Q: iPod shuffle not showing in iTunes

Have you tried resetting the iPod Shuffle with it still connected a USB port located directly on your Mac?

Resetting iPod shuffle

Are you using the same USB cable that you normally use to sync the Shuffle?

B-rock

And you are plugging into a USB port located directly on the Mac? Have you double checked to make sure the connections on each end of the cable are nice and snug?

Are any other devices plugged in via USB?

And again from above:

Are you using the same USB cable that you normally use to sync the Shuffle?

B-rock

Have you tried rebooting and then reconnecting your Shuffle?

Can you think of what may have changed on the Mac since the last time you were able to success connect and sync your Shuffle?

Maybe work through the remaining troubleshooting in this Apple support document.

iPod not recognized in iTunes and Mac desktop

B-rock

Maybe re-install the latest version of iTunes on top of the existing version on your Mac.

http://www.apple.com/itunes/download/

B-rock