Noise is an open source project to bring VST development to the .Net Framework. The project is in transition from its old home to google.

Before building the solution, you will need to grab the VST Plugin SDK from Steinberg at http://www.steinberg.de/331+M52087573ab0.html

(Read the readme.txt in the root Noise directory for more details).

I haven't had much time to work on Noise recently, but hope to pick it up again soon. Meanwhile you might want to check out VST.Net - another project which is also trying to support VST on .Net: http://www.codeplex.com/vstnet