Big Mamma: http://newyork.craigslist.org/brk/sys/2248759672.html
Old Mamma: http://newyork.craigslist.org/brk/sys/2248859241.html
Big Mamma was purchased for a recent shoot and now I'm flipping her because I need a computer with a PCI slot and larger monitor (something 99% of people don't need). She is not the most recent upgrade but the October, 2010 upgrade. That's important to keep in mind.
Old Mamma is old but has been very reliable to me over the years. I'm keeping all my software on her to sweeten the deal so if you're broke and in need of something "good enough" she'll suit you well.
...feel free to haggle with me for either. I'm not sure how the prices I've listed compete with what else is available.
Just in case your curious: Mac Tower or 17in Mac Pro for WORK and an 11 in mac air for PERSONAL is where im headed:)