I hadn't realized that AMD had introduced the last chip, the FX-60, to inhabit Socket 939 until conversation over lunch with my friend Chris Morrell. The FX line has always been AMD's high-performance, price-is-no-limit processor line and the latest and last chip is no exception. The equivalent of the FX-60 on the regular AMD line is the Athlon 64 X2 5200+, which is also dual-core and was recently released. The FX-60 features two processors on a single die (dual-core), each with 1 MB of L2 cache (2MB total) and an effective clock of 2.6GHz. The FX-60 is your last chance for all out performance on the PC until AMD unveils the AM2 socket (revamped 940 pin), which ushers in DDR2 technology to the AMD platform.
Tom's Hardware labeled it as the M2 socket that will be released in the near future but TheInquirer seems to think otherwise. Tom's Hardware has an in-depth review of the FX-60 along with some history of the older FX chips. They even overclock the FX-60 to 3GHz with liquid cooling.