The Mono Project is an open development initiative sponsored by Novell that is working to develop an open source, UNIX version of the Microsoft .NET development platform. Mono was originally begun by Miguel and the folks at Ximian, and then Ximian was later purchased by Novell.
Mono includes a compiler for the C# language, a Common Language Runtime (CLR) for the Common Language Infrastructure (CLI) and a set of class libraries. The runtime can be embedded into your applications. It implements both ADO.NET and ASP.NET.
An IDE called MonoDevelop is available for Mono. It is a port of SharpDevelop. So far it is still in its early stages, but it is functional.
Mono Project news
On the 30th June 2004 Novell and the Mono project developer community released Mono version 1. For more information see the release notes.