Another common problem with ASP.NET sites today is long, ugly URLs (look at any MSDN article for example).  While URL mapping can certainly be done today using either Application_BeginRequest in the global.asax or a custom HttpHandler, ASP.NET 2.0 makes common mappings simple by adding support for them to the web.config file.  A new configuration section, urlMappings, will allow individual 'fake' URLs to be mapped to their actual (probably much longer) counterparts.  A very common use for this would be to eliminate navigation-specific querystring data, such as that used by the IBuySpy or Rainbow portal applications.  Instead of having users navigate to http://yourwebsite.com/Default.aspx?tabid=0 you can point them to http://yourwebsite.com/Home.aspx, and specify the mapping in the config like so:

<urlMappings enabled="true">
  <add url="~/Home.aspx" mappedUrl="~/Default.aspx?tabid=0" />
</urlMappings>