Trevor,
I've modelled quite a bit of my business around eBay's affiliate datafeeds - it's powerful, but I must admit it took a little work to setup. With eBay, there are two key approaches to tapping into their feeds, Javascript and XML. The Javascript path is dead simple, but you're pretty much stuck with their layout (but works for most people). With XML, you can pretty much do what you want.
Here's a sample of (someone's else) Javascript site:
http://www.handbags-and-purses.org/
And here's one of my XML sites that the above site *inspired*:
http://www.handbagszone.com/
After some consternation, I decided to bite the bullet and go the XML path using PHP. One of the key reasons I initially choose XML was to leverage the updated content for the search engines bots (since javascript is ignored by SE) - the auction data is updated in real time and is always changing. I also knew I could leverage the same PHP code base over all my sites.
My favorite feature of eBay's affilate programming interface is the ability to insert tracking codes into the affiliate URLs. This is *key* for me since I track the keyword page they bought from and the specific Adwords campaign that got them there. It would be a crap shoot without this tracking feature...
Check out
http://affiliates.ebay.com/ for program details. If you decide to go for it, I'll be happy to give you some code examples to get you going...
p.s. Teli's datafeed tool looks pretty cool - I checked it out sometime ago and was really impressed with it.