The eBay Selling Starter Kit for ASP.NET 2.0 provides a fully-functional sample that enables you to build a custom application to list items, monitor auctions, integrate eBay search and perform inventory maintenance.
You can download it for free directly from eBay: http://developer.ebay.com/windows/starterkits/ There is also a good MSDN article describing it that you can read here. Note that it works perfectly well with the free Visual Web Developer Express Edition development tool.
Below is a sample screen-shot showing active auction listings:
You can learn all about the application and download the source for it here.
If you are looking for a ASP.NET 2.0 Commerce Starter Kit with PayPal integration, you should also check out this Starter Kit here.
Hope this helps,