CMS 16GB (4X4GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I5 3.6 21.5-Inch (Mid-2010) - A28 at Amazon.com
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Timetec Hynix IC 8GB Compatible for Apple DDR3 PC3-8500 1067MHz /1066MHz SODIMM Memory Upgrade for MacBook 13'' Mid 2010, MacBook Pro 13'' Mid 2010, iMac 27''Late 2009, Mac Mini Mid 2010 (8GB) - Newegg.com
A-Tech 2GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010, Mid/Late 2011), Mac mini (Mid 2011) | DDR3 1333MHz PC3-10600 SODIMM 204-Pin Memory Upgrade - Newegg.com
Timetec Hynix IC 32GB KIT(4x8GB) Compatible for Apple Late 2009 iMac 27inch DDR3 PC3-8500 1067MHz/1066MHz CL7 204 Pin 1.5V Dual Rank 2R8 Memory Module RAM Upgrade for iMac 11,1 (32GB KIT(4x8GB)) -