MUSIC Factory Outlet (AKA Behringer's parent company) has refurbished XENYX UFX1204 [ebay.com]
12-Input USB/Firewire Mixer for $199 with free shipping.
I use this mixer for podcasting and cannot recommend it enough. What sets this mixer apart is multi-track recording. Most USB mixers only record the main mix but this mixer will record all 12 channels, the 2 aux buses, and main bus. That makes it basically like a 16x4 audio interface which is perfect for podcasting. You can do a mix/minus setup for Skype calls while still having up to 4 XLR mics in the studio and record each person separately to make editing easier. The only other mixers under $500 I know of that do this are the Presonus StudioLive AR8/AR12 ($399/$499), Allen & Heath ZEDi-10 ($199), and Soundcraft Signature 12 MTK ($449). I've tried the PreSonus mixer and found the preamps a little under powered. The A&H mixer looks like a steal at $199, but it only has a 4x4 audio interface unlike the rest of these. And the Soundcraft by all reports is in another league compared to these but it's also in another price bracket costing twice as much as the Behringer and A&H mixers. Sorry about the long rant, but this is a great mixer and a great price. The normal refurbished price is $240 (but has been $280 for a few months now) and the retail price is $399. My refurb from the factory outlet was like new and includes a 3-year warranty.
Refurbished Behringer MINIAMP AMP800 4-Channel Headphone Amp - $52 [ebay.com]
OOS - Refurbished XENYX UFX1604 16-Input USB Mixer - $299 [ebay.com]