There is coseats.com which gets travellers linked up with people driving. Looks like it's just within Australia.
A bit like pre-arranged hitch-hiking with the passenger putting in some money for fuel. Accomodation and meals would need to be discussed.
I used Coseats to get a passenger on my way from Canberra to Perth, picking them up in Port Augusta, South Australia.
Worked well, too far to drive on my lonesome.