8GB 2x 4GB DDR3 Memory RAM for Apple iMac Intel Core 2 Duo 21.5inch (Late 2009) | eBay
Memory Upgrades for Apple iMac 2011 Up to 32GB
Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and iMac 11,1 at Amazon.com
Memory Upgrades for Apple iMac 2009 - Up to 32GB
NEMIX RAM 4GB (1X4GB) DDR3 1066MHZ PC3-8500 MacBook Pro (Late 2006 - Late 2008) Pre-unibody iMac (Early & Mid 2009) iMac (Late 2009) MacBook Pro (Late 2008 - 2010) Compatible Memory at Amazon.com
Benefits from RAM upgrade to Late 2009 iMac | MacRumors Forums
Apple iMac 21.5" 3.06GHz Intel Core 2 Duo 8GB DDR3 Ram 500GB HDD Late 2009 | eBay