How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
iMac | 3.06 GHz Core 2 Duo | 27 Inch | Late 2009 - Techable.com
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
Apple iMac 27" - Early 2009 Reviews, Pros and Cons | TechSpot