I am putting this here because right now at least, there is one Foster's-related item up for auction.
sorenrogers.com
This is a fund raising site for a little boy suffering from seizures. It seems that Craig McCracken, along with other animators or at least studios, have donated items for eBay auctions to help this little guy. There is a link on the sorenrogers page to the eBay store, where you will find an uncut sheet of Coco Cards signed by Craig.