Atsushi Enomoto blogs about the work involved in bringing LINQ to Databases to Mono.
The effort was a joint collaboration between the awesome DbLINQ developers, Pablo Iñigo Blasco our Google Summer of Code Student and Novell's Atsushi Enomoto.
The DbLINQ developers had created a general purpose LINQ provider that could be used with database providers other than SQL Server. They also relicensed their code a few months ago to the MIT X11 license to allow for integration with Mono's code base.
Read Atsushi's description of how the effort was put together and how DbLINQ is being refactored to become a full System.Data.Linq implementation and still provide the foundation for third-parties to easily create database LINQ providers.
DbLINQ is a great project, and it needs your help to complete the effort.