Recently, I ran into DotNetKicks, a site dedicated to provide Digg-like functionality for articles, blog posts, and general news surrounding the .NET platform. One of the cool things DotNetKicks sports is... extensionless URLS! Instead of http://www.dotnetkicks.com/docs/about.aspx, DotNetKicks leaves off the .aspx: http://www.dotnetkicks.com/docs/about.
Benefits
There is a wealth of benefits you can get with extensionless URLs. For starters, search engines are happy. People are happy they don't have to worry about extensions (such as .html, .aspx, .htm, .php, etc.) or even QueryStrings (EX: http://foo.com/somepage.aspx?foo=bar). It just gives the website a cleaner feeling, I think.
Extensionless URLs on the net isn't something new. Ruby On Rails automatically does this for you. But for those .NET-ers out there, there is an easy solution (sort of... see the next part)... URL REWRITING! I have been using URL rewriting for quite some time. I personally think it is an excellent way for any .NET web application to run. I recommend using UrlRewriting.NET. It is easy to setup and costs you NOTHING!
Now for the bad news
IIS6 currently doesn't support extensionless URLs. If you are on a shared hosting environment (like EagleEnvision.NeT is), your hoster will most likely not install the necessary mappings for extensionless URLs to work. However there are 2 solutions. One is using IIS7, which will be released later this year. The other is to do, what's called, Wildcard mapping (see this URL for instructions). What that basically does is tells IIS6 to map all requests through ASP.NET.
Conclusion
It will be nice once hosters upgrade to IIS7. It will really be cool when extensionless URL functionality can be provided to the masses!
Microsoft is optimistic about adoption of IIS7. Let's hope that holds true!