Apple Memory Module 1GB 667MHz DDR2 FB DIMM ECC (2x512MB)
Used but fairly new. Rock solid RAM. My Mac Pro has *never* KP'ed once with the 1GB kit since I bought it in late October.
Apple sells the kit for US$300...I'm letting it go for $219. I believe it's also the only RAM Apple will honor if you've got AppleCare.
Free shipping if you're in Canada or the US.