How do you set up IIS so that when someone types in www.yourdomain.com it changes to yourdomain.com without the www.?
one example of this is www.twitter.com
You have a few options. If it's IIS7, definitely consider URL Rewrite. For IIS 6 I would consider ISAPI Rewrite (www.isapirewrite.com).
If you use your own server, setup a redirect site with www.yourdomain.com for the bindings and add a full redirect to yourdomain.com. Basically have 2 full sites.
As you could handle it from code too, although the previous options are usually better.