I've recently been working extensively with 2 ORMS. Subsonic and Nettiers. Both really good ORMS. My favourite though without a doubt is Subsonic written and designed by Rob Connery who just coincidentally now works for the ASP.NET team at Microsoft...
You gotta love it. Community Server 2007 .... open source. So much source to devour. The problem is, you never know where to start. Spending days studying masses of open source code is only worthwhile if you have a lot of time to understand how the project...