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
Install memory in an iMac - Apple Support
4GB -2x2GB Memory Ram Upgrade for 20" Apple iMac-7.1 2.0GHz Core2Duo Mid 2007 | eBay