Multi-threaded programming

This is something I've been curious about for a long time but haven't really had the chance to look into. Thanks to this tutorial at LLNL, I've discovered that it's actually quite easy to do simple multi-threading with POSIX threads -- all you really need are basic C programming skills and a basic concept of how processes are managed by a POSIX operating system. The API is easy to learn, and there is MUCH less overhead compared to multi-host parallel programming. On SMP machines, it is probably much more powerful than using a full parallel enviornment like MPI.