Only been using this site a day, but have a couple of suggestions:
1) 'Dutch' Buy It Now listings- allow the number of items one buyer can get. Say you have 6 apples to sell, only let each registered buyer buy a maximum of 2.
I know this goes against the rules of business, but there are a few benefits. Say I wanted to attract new customers with a GREAT deal, but as soon as I put my listing on, someone buys up my whole stock. In the example above, I would rather have 3 grateful customers than one greedy one
This also give me a better chance to build feedback.
2) In the auction listings, it look odd that the 'description' part is wider than the rest of the auction contents. Looking at the code, you have set it at 998px wide, whereas the other parts are 660px (or somewhere close to that). If this is done to gain attention to the description part so people read it, I don't think it works and just looks odd. Fine something to fill in the gaps on either side, like sellers other auctions?
3) Allow users who know HTML and can put in their own pictures in the description to have a gallery picture, but not display it in the main listing. This saves having to scroll past the picture to get to the description.
I'm sure there are more things... I like the look of the site- shame it doesn't use CSS and is bogged down with tables.