LG TU/CU720 Shine phone - $30

This phone was previously used on the Rogers GSM network in Canada, so it is suitable for any GSM network here in the States (e.g. AT&T or T-Mobile). It wasn't used for very long, so it is in great condition.

The phone is still locked, but unlocking costs very little ($10-$15) and is easy to do. Here are a couple of links with costs and instructions:
http://www.unlockallcellular.com/tu720-shine-unlock-code-np-58771.html
http://www.youtube.com/watch?v=N0sO4AIY5jU

Google Shopping tells me these phones are going for $60-$100 depending on their condition (used, refurb, new, etc.), so I think $30 is a pretty good price given that it needs to be unlocked.