Two recommendations:
First I would make the category navigation links a little larger at the top - even at 640x480 an old man like me has to squint to see whats there
Second - I would get rid of the redirect number sequences for all your banners and pics - make them straight static urls - the reason for that will be down the road to get listed in the SE's - you want the bots to be able to crawl your pages and some of those links are so long the robots will get totally confused and just stop - also I would put mouseovers on the sponsor links to show just the main url of the paysite without any codes displayed - surfers will feel more comfortable about it and click more often