I just enabeled VPN in my DD-WRT router and it was quite easy. First I set up a free account with dyndns.org since I have a dynamic IP address from my cable company. My home network is now assigned tev9999network.dyndns.tv. (example - don't bother trying to hack me there).
In DD-WRT, I entered my dyndns account info and password. Now the router will automatically update tev9999network.dyndns.tv to whatever IP my cable company assigns on a day to day basis, so I don't have to remember I was at 134.111.25.145 yesterday and hope it is the same.
You also enable PPTP under the services tab and assign the user names and passwords you need.
I also configured my home theater PC to "Wake on Lan", so I can connect to it remotely if I want to get a file off my hard drive. I can even get to it from my Android phone. I'm still figuring out how to control Windows Media Center remotely. I also have not yet tried watching my recorded TV content over VPN, but I don't think it will be a problem.
The other advantage of DD-WRT is that it made my flakey, constantly dropping, D-Link router rock solid after I got rid of their crappy firmware.
DD-WRT is available for many routers now, so you may not even need to buy any hardware.