TheServerSide.Net has a list of ORM tools.  Missing from their list (but posted by users in the feedback) is Gentle.NET and WilsonORMapper. I must say its quite a list ! No wonder Ted Neward calls ORM the "Vietnam" om .NET (huge amounts of work with little progress).

There's 2 things I want to say about ORM:

• I think that a tool that generates a bunch of code is not a real ORM tool. If I wanted to generate code for data access I'd use CodeSmith and do the templates myself [In fact I've done this before and it was quite trivial]. So for me ORM is dynamically generated parameterized SQL.
• Secondly, I choose nHibernate for those who'd like to know :) Brilliant tool. Take the time to learn it, you won't be disappointed. [The documentation for Hibernate, the java version, is very good, so I suggest you use that as a reference until nHibernate has their own.]