Found at CodePlex
The Web Solutions Platform (WSP) event system is a general-purpose distributed publish/subscribe event system designed for high performance and low latency. Publish/subscribe is a common communication pattern though there are many variations to solve different scenario requirements. The event system provides the developer with a class library paradigm for publishing and subscribing to events. The events are developer-defined .Net classes which sub-class from the base event. This makes the system both easy to use and very extensible.
Get the code here
Documentation (White Paper) here