Just a couple of ideas (but they rely on eBid management's involvement too):
1/ How about a prize supplied by eBid for the winner of the monthly Buddy Points chart? I know the Buddy Points are a good reward as they are, but a prize (an iPod shuffle, extra Buddy Points, some vouchers etc..) could give more incentive to hit that top spot and, therefore, bring more people to the site.
2/ What about a monthly 'High to Low' Buddy Points auction? People who perhaps have lesser Buddy Points feel they are in with a chance of winning a great item (Sat Nav, PSP etc..) for whatever the lowest *unique* bid is made in Buddy Points to 1 decimal place (7.9 points for example). The bids would all be kept secret until the auction ended. Again this could encourage people to build up their buddy points and would potentially be a headline-grabbing story at the same time.