My friend Mario in Costa Rica sent me a short email about NGINX (pronounced engine-X). It is a web server and a bit more written by Igor Sysoev in Russia. Clearly, it isn't for everyone but if you have a very busy site that needs load balancing and some other performance stuff, it looks pretty interesting.
A lot of the documentation is in Russian but, is a Wiki and other information in English. The overview page is a good place to start. You will find, for example, "10,000 inactive HTTP keep-alive connections take about 2.5M memory". Sounds like it might actually work with a high-volume site.