UPDATE: Qyoto has been obsoleted. There's a replacement project in development called QtSharp.
Qyoto makes it possible to develop Qt applications using C#, or any other .NET language. Qyoto uses SMOKE, and offers access to almost all Qt classes. It is free and open source with the LGPL license.
Qyoto is part of the kdebindings module in the KDE git repository.
$ git clone git://anongit.kde.org/assemblygen
You can also browse the source online.
Pre-built binary packages are available in the following distributions: