A-Tech for Apple 6GB Kit (1x2GB + 1x4GB) DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook (Late 2007, Early 2008, Early 2009), MacBook Pro (Mid 2007, Early 2008), iMac (Mid 2007) - Memory RAM Upgrade at Amazon.com
iMac (2009) RAM & Storage Upgrades
A-Tech for Apple 4GB Kit (2X 2GB) DDR3 1067MHz / 1066MHz PC3-8500 SODIMM iMac (Early/Mid/Late 2009, 20/24 inch, 21.5/27 inch), Mac Mini (Early/Late 2009 Mid 2010) Memory RAM Upgrade at Amazon.com
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
How to Upgrade the RAM in Your iMac
iMac (2007-2009) Memory Installation Video - YouTube
iMac (Early 2009) | Low End Mac
iMac 21.5" Late 2009 (10,1) - CPU Upgrade E8600 | MacRumors Forums