In case you missed it, memcached 1.2.5 was released on March 3rd. I think it's pretty safe to say that Memcached is one of the corner stones of many of the most trafficked sites on the internet. It allows them to work at a very large scale without a budget approximating the cost of flying a mission to Mars. If you haven't yet begun to investigate memcached, then do so because no matter what platform/framework it is that you are running, this might be something for you to take a look at implementing to improve your scalability in various ways. Take your time though and do your research, it's not as easy as sometimes if first seems.

Enjoy!