I upgraded my new 2.8ghz iMac from 2GB to 4GB RAM. So I'm selling the two "Apple" original 1GB sticks of RAM. PC5300 SO-DIMM. I upgraded the RAM in my iMac 2 days after receiving, and the stock RAM functioned flawlessly.
The manufacturer is Samsung and yes, this RAM should work for all of the Intel iMacs, Macbooks and Macbook Pros.
Looked around and found that OWC (where I purchased my 4GB upgrade) has a kits of 2X1GB Sticks for between $48-$80 depending on the supplier (and that does not include shipping). I'll assume that the RAM that came with my 2.8GHZ from Apple is equivalent to the higher-end RAM offered by OWC.
See OWC prices
$40 shipped and Paypal'ed (not really negotiating in this)