What is the best way to join 2 offices on a network

Hi Everyone

I am looking at the best way to join 2 offices together on our network.

What we would like to do is to put in a leased line between the two. We want them to be able to use our exchange servers and we would only like to put in two servers which will be a pdc and an ISA server.

Does any one have any experience or better suggestions.

Thanks