iMac Intel Memory Wrapup:
The iMac Intel Core Duo uses laptop RAM (DDR-2 667 MHz SODIMMs), and is completely unlike the preceding iMacs. You cannot use any memory from any prior Mac model.
It has 2 memory sockets an no memory soldered on. It delivers with either a single 512 Mb SODIMM or a single 1 GB SODIMM depending on model.
You can add a 512 Mb or a 1 Gb SODIMM to that -- RAM does not have to be matched. In order to take a 512 Mb machine to 2 Gb, you will remove the 512 Mb and install 2 x 1 Gb SODIMMs. You can then sell the 512 Mb to a MacBook Pro owner, because the intel Core Duo 'powerbook' uses the same memory as the iMac Core Duo.
If you are in the USA I recommend
Data Memory Systems who has the RAM in stock as of Jan 12 for US$108 per 1 Gb SODIMM, which is a great price. Crucial has it listed for about US$130, Kingston hasn't listed it yet.
Thanks
Trevor
CanadaRAM.com