Nomad Wiki

NomadWiki.org | Info and tips for nomads about shoestring budget traveling

Free Hospitality

BeWelcome.org | Invite travelers to your home, find hosts all over the world, and become part of our multicultural hospitality community
Couchsurfing.org | Free hospitality exchange like BeWelcome
SustainableCouch.org | a project which aims to bring some aspects of ecological, social and economic sustainability to the hospex world

Free Volunteering Hubs

ThePoosh.org | Sustainable building projects looking for volunteers
ProjectDirt.com | UK’s most active network connecting and resourcing community projects.

Hitch-Hiking

HitchWiki.org |  Information about hitchhiking and other ways of extremely cheap ways of transport.
HitchBase.org | Similar to HitchWiki
More related links here: http://hitchwiki.org/en/Websites

Cycling

bikesurf.org | Very cool project that provides free bicycles for travelers visiting a city. You can start your own cell using their online platform
warmshowers.org | Free worldwide hospitality exchange for touring cyclists. People who are willing to host touring cyclists sign up and provide their contact information, and may occasionally have someone stay with them and share great stories and a drink

Car Sharing

blablacar.com (International)
carpooling.co.uk (International)
mitfahrgelegenheit.de (Germany)
gomore.dk (Denmark)
hitchhikers.org Hitchhikers.org (Europe)
viajamosjuntos.com Viajamos juntos (Spain)
taxistop.be Taxistop (Belgium)
prevoz.org Prevoz (Slovenia)
kyydit.net/en (Finland)
kimppa.net (Finland)

Volunteer tour guides:

hieverywhere.com

Alternative-Consumerism:

trashwiki.org | Dumpster Diving Wiki
fallingfruit.org | World map of urban edibles with 610.000+ locations
storyofstuff.com
streetbank.com (former justfortheloveofit.org)
en.wikipedia.org/wiki/De-growth
en.wikipedia.org/wiki/Transition_Towns

Others

viacampesina.org | Movement which brings together millions of peasants, small and medium-size farmers, landless people, women farmers, indigenous people, migrants and agricultural workers from around the world. It defends small-scale sustainable agriculture as a way to promote social justice and dignity.