Depends on the model I believe. Mine (1.5GHz) has one RAM slot and 256MB soldered onto the motherboard. The max RAM you can buy is a 1GB stick, giving it a total of 1.25GB.
Go to crucial ram's website and use their search function to find the RAM you need. I bought mine from newegg.com.
EDIT: saw you figured it out... I trust newegg, but crucial or OWC are also great from what I have heard.