Ports Needed Open for Windows VPN

You were able to create a dial-up VPN connection between Vista and Windows Web Server 2008 without the Network Policy Server role? If so, I'm curious as to what the subnet/IP looked like to the client in that scenario once the tunnel was up.

If you have a VPN up, then you've transferred your problem domain from one of VPN to one of routing. I'm pretty confident that you'll be able to bridge connections using the Web edition and that you can also use Internet Connection Sharing. If not, there are cheap and possibly free "internet sharing" programs available (NAT32).

This assumes that your client machine somehow has an IP on the server's (internal?) network.

Also, when you say Internet traffic, it's possible your definition may include only traffic that is proxy-able. In which case you can shift the domain again from routing to proxying, and use a free proxy server bound to the IP on the other end of the tunnel.

If RRAS is installed and configured on a machine that is not a member of the domain, it will use the local accounts database rather than Active Directory, the setup process is the same.

With regards to the protocol, they are both good options. Both make use of certificates, SSTP gives you the advantage that it uses port 443, which should mean you have minimal firewall issues. L2TP operates at the IP layer, whereas SSTP operates at the TCP layer, if that has any bearing on your choice.