HI MegaCGI,
There are two ways of implementing this, one of which is through software on the servers themselves. Windows 2000 Server and Windows Server 2003 both ship with load-balancing utilities, as do most Linux implementations, and there are several third-party products around too.
The other approach is to build a load-balancing cluster using an external switch not a regular Layer 2 product, but one capable of making routing decisions at Layer 4 . The switch is positioned between the cluster and its connection to the local network or outside world and routes request at wire speed for maximum throughput.