I just came across a fantastic series of blog posts from Ken Cline at “Kens Virtual Reality Blog” that ties up pretty much everything you will ever need to know about configuring networking in ESX 3.5 \ ESXi. No doubt there will be some significant changes in ESX 4 but even so this is a great resource. There are 5 parts to this so far, all the earlier items which explain all the background detail are linked from this fifth part where Ken makes some hard and fast recommendations around how to tie it all together to create robust and effective ESX network design decisions.
He covers everything from the basics of creating vSwitches and Port Groups, VLAN tagging – clearly explaining what VGT\EGT\VST tagging variations actually mean and how they are enabled, load balancing options and their usefulness (or not) especially in relation to 802.3ad \ LACP\PaGP, NIC failover especially with regard to Beacon Probing and Link State Tracking on your physical switches, security options (Forged Transmits\MAC Address changes, Promiscuous mode) and a lot more. Definitely recommended for anyone who either builds or wants to understand ESX installations.