A-Tech 16GB Kit (2x8GB) DDR3 1066MHz / 1067MHz PC3-8500 SODIMM RAM for Apple MacBook (13 inch, Mid 2010), MacBook Pro (13 inch, Mid 2010), iMac (27 inch, Late 2009), Mac Mini (Mid 2010) at Amazon.com
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
iMac (2007-2009) Memory Installation Video - YouTube
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
Install memory in an iMac - Apple Support
Apple iMac 27" Late 2009 i7-860 2.8GHz 16 GB RAM, 240GB SSD, Radeon HD 6970M 1GB | eBay
OWC 16GB (4 x 4GB) PC8500 DDR3 1066MHz SO-DIMMs Memory Compatible with iMac 21.5" and 27" (October/2009) at Amazon.com