I want to provide some dynamic content like an rss feed, so when they go to mydomain.com/fishcake.rss it runs some code on the server to generate it and returns it back.
I am guessing maybe an ashx file and something in the webconfig to associate it with the path I want, but I’m not totally sure. Can you help?
Although the two answers until now are both good, I think your question is more about the dynamic part, rather than the feed structure itself. And you actually answered that yourself. The ASHX file is called an Http Handler, and that’s the way to go about delivering dynamic content. Here’s some more info:
http://msdn.microsoft.com/en-us/library/ms972953.aspx