disruptor-net
If you are concerned by performance, you will probably have heard about LMAX and their disruptor pattern. If not you should have a look to this video and to this white paper first.
LMAX team released the concurrency framework at the heart of their system about one month ago and I decided to port it to .NET.
The source code, unit tests and performance tests have all been ported to .NET and current trunk is in sync with latest Javav version. Performance tests show equivalent level of performance for Java and .NET versions.
If you are interested you can have a look to the disruptor-net project on google code and participate to the discussions on the .NET discussion group or the Java discussion group
