A neat video on a simple MVC site structure that includes PayPal IPN:
http://www.asp.net/mvc/videos/mvc-1/aspnet-mvc-storefront/aspnet-mvc-storefront-part-22-restructuring-rerouting-and-paypal
Direct link to his IPN controller
https://mvcsamples.svn.codeplex.com/svn/trunk/Kona.Web/Controllers/PayPalController.cs
MVC/C# Example:
http://www.markstraley.com/Code/PayPalIPN
Thanks @Earlee!
