4GB iMac Memory for Early 2006 to Mid 2007 Models 4,1 4,2 5,1 5,2 6,1 and 7,1 (2GBx2)
OWC 4GB PC5300 DDR2 667MHz SO-DIMM Memory RAM Upgrade Compatible with MacBook (Late 2007/Early 2008), MacBook Pro (Mid/Late 2007, Early 2008), & iMac (Late 2007) with Core 2 Duo CPU (OWC5300DDR2S4GB) at Amazon.com
A-Tech 4GB Kit (2x2GB) RAM for Apple MacBook Pro (Late 2006), MacBook (Late 2006, Mid 2007), iMac (Late 2006), Mac mini (Mid 2007) | DDR2 667MHz PC2-5300 SODIMM 200-Pin Memory Upgrade - Newegg.com
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
A-Tech for Apple 6GB Kit (1x2GB 1x4GB) DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook (Late 2007, Early 2008, Early 2009), MacBook Pro (Mid 2007, Early 2008), iMac (Mid 2007) - Memory RAM Upgrade at Amazon.com
6GB Memory for 2007-2008 MacBook Pro, MacBook, and iMac