Adrian Dimcev, a big ISA Firewall fan, has put up a new ISA Firewall information site. Adrian has a lot of useful and detailed information about the ISA Firewall and how to setup the ISA Firewall in a virtualized environment for testing purposes. In addition, Adrian is putting together a very detailed series of documents on how the ISA Firewall's L2TP/IPSec server and protocols work. I highly recommend this site and it's worth your time to check it out.
Visit Adrian Dimcev's site at: http://www.carbonwind.net