I've worked with SubSonic in a recent project and it's an absolute pleasure to work with. Zero configuration for ORM mapping and low learning curve.
The learning curve is about 1 day if you put your effort into it. If you need longer than 1 day either IM me or leave a comment in my blog and I will write you something that will get you through the learning curve quickly. Check it out at subsonicproject http://subsonicproject.com/
Sorry for digging up this old post but I thought it appropriate to leave a note in this post since other people has left good suggestions.