I recently asked a question similar to this one.
After I realized that Hamachi can be used on the Pi, a use for the VPN popped up - SSH.
Is it be possible to use a VPN to access my Pi via SSH? Personally, I see nothing that would stop this from being occuring.
As long as the Pi and your computer are in the same Hamachi VPN network, it will work.
As an alternative, you could create a port forwarding in your router that forwards Port 22 (SSH) to the IP of your Raspberry Pi. Then you could connect directly from the outside. (I'd suggest to map SSH to a different port than 22 though, for security reasons.)
pptpd worked for me. As suggested by Danilo you would need to port forward on your router if you are going to connect to the pi from the internet. Once you are connected over vpn ssh would work.
