A-Tech for Apple 2GB DDR3 1067MHz / 1066MHz PC3-8500 SODIMM Memory RAM Module for MacBook, MacBook Pro, iMac, Mac Mini - (Late 2008, Early 2009, Mid 2009, Late 2009, Mid 2010) Models at Amazon.com
iMac (2009) RAM & Storage Upgrades
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
Install memory in an iMac - Apple Support
Can the Late 2009 27" iMac handle 32GB of RAM? | MacRumors Forums
Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 RAM for Mac Book (