Gentle.NET is an object persistence framework for .NET written in C#. It features automatic SQL generation and object construction, an SQL factory for creating custom queries, DataView construction helpers, and reasonably complete docs. It currently supports PostgreSQL, MySQL, MS SQL Server, and SQLite. It includes VS.NET project files for building under Windows, and a Makefile for building with Mono.
Version 0.9.5 adds support for Operator.In/NotIn constraints and includes a number of fixes and code cleanups over previous releases. MySQL is now fully supported under Mono.