CouchSurfing

CouchSurfing http://www.couchsurfing.org is the largest international hospitality exchange network. It is used by 234 countries with over 1.6 million members. It started in 2003 by Casey Fenton from San Francisco. It almost crashed a few years ago when a computer problem erased much of the site, but members fought to keep the site open and it flourishes today.
Couchsurfing reminds me of a cross between hostelling (which I did from Maine to California) and a college exchange program. Here people go to the site and register for free. Then they fill in the information (place, age, gender, dates) that they are looking for and off they go. The more specific the information, the closer the match. There is no money exchanged and arrangements are made ahead of time. The traveler can provide food for the host in exchange for the accommodations if they want to.
There really are no other sites quite like this one. Hostelling uses a small fee to stay in a designated location. Other sites are more travel related and users provide feedback, information and photos of places they have traveled to.
I loved hostelling across the country. Now I am married and probably would not use couchsurfing. If I were a college student, I would certainly consider this. My other thought is, I remember it took me until age 30 to hostel alone because I am female. I think it is easier for men. I would like to believe that has changed, but there was one instance in 2009 when a female stayed with a male in another country and claimed he raped her. He denied it, but went to jail for ten years. Now the website suggests women stay with women if they have any safety concerns. Sadly, I agree.