I set up a web server cluster with Ultra Monkey one or two months ago. I'll write a tutorial about it as soon as I find the time. Until then you should check out these web sites:
http://www.ultramonkey.org/3/topologies/
http://www.linuxvirtualserver.org/HighAvailability.html
If you are in need for a high-availability storage solution:
http://www.howtoforge.com/high_avail...drbd_heartbeat