The Polish Way
The third travelling option is for those who are comfortable with hitchhiking. I call it the Polish way; this is because almost everyone I know who does hitchhike, is Polish or from an ex-USSR country.
I personally am weary of this because I have never done this and have seen way too many crime shows where people end up dead but I certainly know many people who continue to travel through hitchhiking only, and if someone experienced is with you, that is the best way to go.
There are websites set up for people to travel together and since everyone has to be registered it is pretty safe. The only thing is since this is car sharing, you will have to pay a little bit for petrol/gas.
The other option is www.hitchhikers.org where people submit their trips and you can catch them on the highways, rest stops or get in touch via phone.