After battling VPN on linux for over a week, I have what I think is the best solution out there for those of you using linux firewalls as your primary home routers. For completeness sake, I'll post what I did to connect my VPNs as tunnels on my linux router instead of using pptp-config or clobbering my default gateway. While this isn't the easiest approach, it is most defiantly the easiest to use when you have more than one PC on the network and your VPN only allows for one login.
I was once searching the internet for a NAT script to one of my machines to do my routing. Hopefully, I will be able to explain how to make a simple, fast, and scalable iptables rule set (and all without scripting it++); Iptables in linux does not have to be as complicated and obscure as many sites and people make it out to be. It's all really just a complex set of simple rules.