mac usergroup.
e.g. in chicago they have "the rest of us".
sell it, definitely. put an announce to the local mac usergroups if you have them around, and to this site's classifieds too, and ebay, anywhere you can. 256 mb ram is something that someone will buy for sure, and you would have no problem selling it.
never throw away ram, even if it's for older models, sell it, or change it for soemthing else. i had a 32 mb module of ram for laptop lying around, and i just changed it for a dvd i want and that i can't buy in this country!