Links on the Url Rewriting for ASP.NET (IIS5,6)

Good starting point, ScottGu:
http://weblogs.asp.net/scottgu/archive/2007/02/26/tip-trick-url-rewriting-with-asp-net.aspx

ISAPI filter solutions

Helicontech

Commercial solution for ISAPI url rewrite filter: http://www.isapirewrite.com/
Free Lite version is available.
Very good place to browse around to understand benefits of url rewriting.

Ionics Isapi Rewrite Filter

Open source (MS permissive licence) http://www.codeplex.com/IIRF

Handling images and css links when employing url rewriting

http://pstatho.wordpress.com/2007/04/17/url-rewriting-with-aspnet-and-handling-images-and-css/