Kingston KVR16N11K2/16 16GB 1600MHZ DDR3 Non-ECC CL11 DIMM (KIT of 2) at Amazon.com
IBM 16GB ECC 4RX4 VLP DDR3 RDIMM PC3L-8500 1066MHz 1.35V CL7 Memory Module (90Y3221) at Amazon.com
OWC 32GB (2 x 16GB) PC10600 DDR3 ECC-R 1333MHz DIMMs Memory Compatible with Mac Pro Early 2009 & Late 2010 'Nehalem' & 'Westmere' Systems and Early 2009 Xserve. at Amazon.com