Though the big names in router/switch appliances (Cisco/3com) are marketing and developing higher level switch devices, the companies specializing in using this for Web server load balancing are relative unknowns:

Alteon

ACEswitch and ACEdirector

Radware

Web Server Director

ArrowPoint

Content Smart (CS) Switches

Holontech

Hyperflow

Some are devices that specialize in intelligent NAT'ing and leave the switching to, well, switches. Others offer full on load balacning and wire level switching, even offering gigabit ethernet uplinks. Some are small 1-U devices, others are big boxes that require a substantial quanitity of rack space.