http://www.ultramonkey.org/
Ultra Moneky is a load balancer similar to the likes of pound and haproxy. It allows multiple web servers to be seen as 1 by the client.
http://haproxy.1wt.eu/
HAProxy is a TCP proxy / load balancer which will work for HTTP and a range of other applications. It advertises a small but expert user base and offers a range of very useful load balancing features. Apparently it competes with pound and ultramonkey.
http://www.apsis.ch/pound/
Pound is a reverse proxy, load balancer and HTTPS front-end for Web server(s). Pound distributes the the load among several Web-servers and allows for a convenient SSL wrapper for those Web servers that do not offer it natively.
