Mapping a wildcard path to a web page?

I currently have a url that looks like this:

www.mysite.com/showWidget.aspx?widgetId=3

I want the URL to look like this:

www.mysite.com/showWidget/3

I've seen this done on other sites, but I can't figure out how to do it. Anybody know?Found one solution: http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=443190