FluentData is a new introduction to the micro-ORM family that aims to be more straightforward to use than full ORMs like NHibernate and Entity Framework. It uses a fluent API and supports SQL Server, SQL Azure, Oracle, and MySQL.
A simple ORM used in StackOverflow titled Dapper.Net was recently released on code.google.com. This ORM specializes in fast generation of objects from SQL query results. Dapper.Net supports mapping query results to a strongly typed list or a list of dynamic objects. The ORM is a single file of less than 500 lines of C# code and is available under the Apache 2.0 License.