HAMACHI WILL NO LONGER BE FREE AS OF 3/16/2014.
You will have to pay 49$ for it.

If you are a lover of all things VPN, a tested and proven VPN that is safe and effective is called Evolve.

https://www.evolvehq.com/welcome
It's really easy to use, and offers a voice chat and everything as well since it's mostly for games.
All you have to do is sign up, sign in, add each other, and 'create party'.

If using as a host, everyone would use YOUR Ip to log in to whatever program you plan on sharing!
That's it!

Me and witchhuntermaoh are using it right now for opencanvas!