Lambda the Ultimate

In this paper we present an abstraction of actors that combines the benefits of thread-based and event-based concurrency. Threads support blocking operations such as system I/O, and can be executed on multiple processor cores in parallel. Event-based computation, on the other hand, is more lightweight and scales to large numbers of actors. We also present a set of combinators that allows a flexible composition of these actors.

Philipp Haller and Martin Odersky also wrote Event-Based Programming without Inversion of Control which was discusssed here last year. You may also remember A Language-based Approach to Unifying Events and Threads (Li and Zdancewic).