I have two offices with dedicated connections at each and I have an ISA server at each setup in integrated mode. I would like to be able to set up a gateway-to-gateway VPN connection between the two ISA servers and have traffic bound for the "internet" at each site routed out and traffic that is destined to go over the VPN to the other site routed correctly as well. Can this be setup with ISA server and if so, any ideas as to how?
Yes, you can do this. Just run the "Set Up Local ISA VPN Server" on one of the Servers to create a .vpc file. Be sure to configure it so that both ends can initiate a connection. After you create the .vpc file, go to the other ISA Server and run the "Set up Remote ISA VPN Server" using the .vpc file you've created.
This will create demand dial interfaces that will allow each of the ISA Servers to establish connections with one another. It will also add static routing table entries so that the demand-dial interfaces are activated when requests for the remote network are made.