iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Install memory in an iMac - Apple Support
NEMIX RAM 32GB (4x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27” , Mac Mini Mid 2011 at Amazon.com
Install memory in an iMac - Apple Support
Timetec 8GB Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 for Mac Book (Mid 2010 13-
OWC a la Carte Upgrades for iMac, including eSATA, Memory, SSD option
How to Upgrade the Main Drive in a 27-inch iMac Mid 2010 (Updated) - YouTube
Apple iMac 27-inch (July 2010) review: Apple iMac 27-inch (July 2010) - CNET