"a set of Java libraries that make using Apache ZooKeeper much easier"

"Visualization tool for webserver concurrency"

"a multithreaded event library for UNIX designed to take full advantage of the manycore, heterogenous, NUMA future"

Interesting thread.

an Objective-C implementation of asynchronous inter-thread message passing

"Late-2009 Concurrency Linkography"

"a language that builds upon the architecture of the Web and principles of isolation, actors, and message-passing to increase application safety, responsiveness, scalability, and developer productivity"

Pity about the dynamism.

Love repeatParallel.

Nice use of annotations.

"an Objective-C implementation of asynchronous inter-thread message passing"

"a Java library that implements our approach to Software Transactional Memories"

A nice introduction to Scala's Actor concurrency model, along with an exploration of some of the general benefits of the language.

Another solution for Erlang-style distributed nodes in Scala, this time using Oracle's Coherence product.

Big multi-core boxes and such, aimed at demanding Java apps.

A look under the hood of Scala's actor model.

"supports the spawning of processes using the API of the standard library's threading module"

"Actors rule. You really should use them in your programs. Especially if your programs do a lot of stuff at once. Seriously, whatever you’re doing besides Actors, it probably sucks."

"an open source Ruby implementation of Google’s Map/Reduce framework". Includes some Rails helpers, etc.

"A fiber is somewhat like a thread, except you have control over when it gets scheduled."

Effectively, "how to change the main loop of an actor" in Scala.

Sort of like Twitter's own as-yet-unreleased Starling, but it has its own protocol rather than speaking memcache's.

"a networking library written in Python. It achieves high scalability by using non-blocking io while at the same time retaining high programmer usability by using coroutines to make the non-blocking io operations appear blocking at the source code level"

Tim Bray sez: "message-queuing systems will inevitably end up at the center of everything serious."

Dave Fayram takes a reasonable tack on a thorny issue.