Redhat has put a lot of effort into making all types of clustering from load-balancing to shared storage and high-availability a core part of its Linux offering. Their solution for a load-balancing cluster with fail over, is the combination of "Linux Virtual Server" (LVS) with "Pulse" for fail over manager and "nanny" for cluster membership management. Personally I don't much like pulse and nanny, mainly because no other distribution uses them, but Redhats load-balancing solution has one advantage, it can be completely, well almost, configured from a web gui.
