Apple Memory Module 4GB 1066MHz DDR3 (PC3-8500) - 2x2GB SO-DIMMs at Amazon .com
Amazon.com: OWC 4GB PC8500 DDR3 1066MHz SO-DIMM Memory Compatible with Early 2009, Early 2010 MacBook, MacBook Pro Unibody Models, 2009/2010 Mac Mini, and 2009 iMac Models : Everything Else
Amazon.com: 8GB 2 X 4GB DDR3 PC3-8500 1066MHz SODIMM Memory RAM for Apple iMac Intel Core 2 Duo 20" inch 24" inch (Early 2009) Equivalent to MC016G/A (PARTS-QUICK BRAND) : Electronics
Amazon.com: OWC 8 GB (2 X 4GB) ram PC8500 DDR3 1066MHz sodimm 204-pin Memory Upgrade Kit, (OWC8566DDR3S8GP), Compatible with MacBook Pro, MacBook, Mac Mini and iMac : Everything Else