If you're thinking about deploying the Edge server role for OCS 2007 R2, then you need to take a look at the Edge Planning Tool.  It takes a lot of the complexity out of planning/configuring an Edge server.

You can download it here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=ec4b960c-3fe2-41bd-abdf-ae89cfcb8c6c&displaylang=en