OWC 16GB (4 x 4GB) PC8500 DDR3 1066MHz SO-DIMMs Memory Compatible with iMac 21.5" and 27" (October/2009) at Amazon.com
Memory Upgrades for Apple iMac 2009 - Up to 32GB
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
Memory RAM Upgrade for Apple iMac 20-inch Early 2009 4GB DDR3 SODIMM | eBay
16GB 2x8gB RAM Memory for Macbook Pro MacMini iMac 2009 2010 DDR3 1066 PC3 8500 | eBay
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
iMac (2009) RAM & Storage Upgrades
Can the Late 2009 27" iMac handle 32GB of RAM? | MacRumors Forums
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
parts-quick 6GB Kit (4GB + 2GB) Memory for iMac 2008 Apple MacBook 2009 PC2-6400 800MHz DDR2 SODIMM at Amazon.com
Install memory in an iMac - Apple Support
8GB KIT 2X 4GB Apple iMac 2.0GHz 20" Mid 2009 2.66GHz 20" MB417LL/A Early 2009 2.66GHz 24" MB418LL/A Early 2009 2.66GHz 27" Late 2009 2.8GHz 27" Late 2009 2.93GHz 24" MB419LL/A Early
8GB -2x4GB Memory Ram Upgrade 20" Apple iMac 9.1 2.66GHz Core 2 Duo Early 2009 | eBay
A-Tech for Apple 4GB Kit (2X 2GB) DDR3 1067MHz / 1066MHz PC3-8500 SODIMM Memory RAM
A-Tech for Apple 1GB DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook, MacBook Pro, iMac, Mac Mini - (Early/Mid/Late 2006, Mid/Late 2007, Early 2008, Early 2009) - Memory RAM Module at Amazon.com
Early 2009 model iMac Computer, DDR3 8GB (2x4GB) RAM Replacement - YouTube