I've been playing with GridGain lately. It's Java, but their API is really sweet. You basically implement a simple interface that defines the map/reduce operations and then your code will be copied to the cluster nodes through a peer-to-peer classloader.
In a recent test I validated a million image urls in less than a minute. In a small EC2 cluster running GridGain.
It's certainly worth looking into if you are interested in that kind of stuff.
It's a shame there are no comments to this yet. If you're relatively new to programming (say, a college student), this is a really cool chunk of code to copy into notepad and figure out.
It really shows you how a tiny amount of code can do some pretty cool stuff.
And even M/R is just a framework for easily parallelizing "embarrassingly parallel" problems and incrementally aggregating the results (instead of in one step). A cool idea for sure, but not ground breaking -- these ideas are as old as parallel computing itself.
Jeff Atwood knew something probably... http://www.codinghorror.com/blog/archives/001114.html