SwitchPipe is a proof of concept "Web application server" or, more accurately, a Web application process manager and request proxy. Backend Web applications are loaded into their own processes, making SwitchPipe language agnostic. HTTP requests are proxied at the TCP level using information extracted from the headers to establish which backend application is being demanded.
Elastica is a highly efficient and extensible, rules-based load-balancer for JBoss that adds dynamic behavior to EJB load balancing. Rules can be defined to redirect EJB requests according to request data, server performance data, or even the time of day
Pure Load Balancer runs in userland, but relies on an asynchronous non forking/non threaded/non blocking architecture. Thanks to Niels Provos' excellent event library, it can also efficiently use the kernel notification mechanisms to never waste CPU time