The idea in the film Pay It Forward is (I think) that we help someone,
unconditionally, and all we ask is that they help three others and so
on - a sort of pyramid helping. What web-sites  / organisations /
casues have sprung up as a result of this film / idea that are
actually putting these principles into practice, in the real world?

Hello dtnl42,

Two good places to start are sites associated with Catherine Ryan Hyde
(http://www.cryanhyde.com/), the author of the novel "Pay It Forward"
on which the film was based:

Pay It Forward Foundation
http://www.payitforwardfoundation.org/

Pay It Forward Movement
http://www.payitforwardmovement.org/

Not surprisingly, these Pay It Forward sites have sets of links to related sites:

"Links" ["People Paying It Forward"]
Pay It Forward Foundation
http://www.payitforwardfoundation.org/links.html

"International Pay It Forward Sites"
Pay It Forward Movement
http://www.payitforwardmovement.org/

For you convenience, I will list those sites here.  I have excluded
several sites that are apparently defunct.

Help Others
http://www.helpothers.org

Favorsunlimited
http://www.favorsunlimited.com/

Giving Game
http://www.givinggame.com/

"payitforwardfoundation" [club for the pay it forward foundation]
Yahoo Groups!
http://groups.yahoo.com/group/payitforwardfoundation/

Extreme Kindness
http://www.extremekindness.com/

Pay It Forward (UK)
http://www.pif.org.uk/

"One Deed One Lifetime" [Singapore]
Channel NewsAsia [MediaCorp News]
http://www.channelnewsasia.com/deed

These sites lead to a couple of other pay-it-forward sites:

Pay It Forward Nederland [Netherlands]
http://www.payitforward.nl/

Students Today Leaders Forever
http://www.tc.umn.edu/~tehv0001/

For additional programs linked to the Pay It Forward Foundation and
Pay It Forward Movement, see:

"Featured Projects"
Pay It Forward Movement
http://www.payitforwardmovement.com/groups.html

"Existing Programs"
Pay It Forward Foundation
http://www.payitforwardfoundation.org/programs.html

Beyond these sites and groups, the answer gets more tricky.  Many
sites state that they were inspired by "Pay It Forward."  However,
they may not be connected to the "official" sources -- so one may ask
how strong their connection is to "Pay It Forward."  I'll leave that
determination to you.

To find many of these sites, you can browse results on Google to the
following searches:

inurl:payitforward "pay it forward"
://www.google.com/search?num=30&hl=en&lr=&safe=off&q=inurl%3Apayitforward+%22pay+it+forward%22

inurl:pif "pay it forward"
://www.google.com/search?num=30&safe=off&q=inurl%3Apif+%22pay+it+forward%22

I hope that this information is helpful.  Please let me know if you
need clarification of this answer.

- justaskscott


Search strategy:

Searched on Google for:

"pay it forward"
"pay it forward foundation"
inurl:payitforward "pay it forward"
inurl:pif "pay it forward"

I also tried other searches, such as searches for links to relevant
sites, as well as viewing defunct sites on the Internet Archive
(http://www.archive.org).