Where to stay?
Probably the cheapest way to stay at a place and a nice way to connect easily with other People :)
2 great websites with al the hostels all over the world. I had good experiences with both of them
Searching for a travelpartner?
Nice website (just german!), simple. I met a person for my Euroepe-Trip here and another one for my USA-Trip. But like I said it's defintex better to meet in advance to be sure that you really have the same ideas of the trip and that you could have a friendly relationship to eachother.
Searching for equipment?
I really can advise to go to the Globetrotter-shop in cologne. So huge. So much fun to try. And competent stuff!
More of my stuff here.
Free guided walking tours:
There are many free guided walking tours in many cities of Europe. For Madrid I really can advise this company. Also because they offer more than 'just' free walking tours. And the guides are so friendly, competent and funny! And the really appear authenitc!