CouchSurfing

Another great way to experience the real culture of the places you are visiting, is by using www.CouchSurfing.com.
With CouchSurfing, you can ask locals, who are members of the website, to host you. Travellers are often offered a couch or a spare bed to sleep on - and it's completely free.
Hosts usually want to get to know their visitors better to get an insight into their culture. This often happens over dinner at the host's house where either the guest or the host cooks a meal from their home country.
Some will take you to a local club or bar for a drink and some will take you sightseeing around town. It is totally up to the host to decide how long they can host you. It all depends on their schedule (some will lend a key to their guests so they can let themselves in) but also about the chemistry between host and traveller. There is, however, never any guarantees of a free spot. You may need to write multiple hosts in each city you visit to find a host who is home and able to have you stay with them.
I have surfed couches in Trieste, Italy and Vienna, Austria. Both times, my hosts were really nice and I spent a lot of time with them in the evening after they came home from work.
This may seem to many as a very unsafe way to travel, but there are certain safety security facilities established by the people behind CouchSurfing. This way you can limit your search for couches to only show members who have been verified by CouchSurfing. You also have the option to read about the hosts before you contact them. Many guests choose to grade and write a line or two about their experience while staying with their hosts. This feature is a great way to find the ideal host for you.