Co-operative Community Challenge
I'm not sure why this isn't being trialed around Cambridge (perhaps the area committee's painting skills were thought not to be up to scratch), but its definitely something that should be supported.
A blog devoted to Co-operation in Cambridge and elsewhere
The idea is that for any one individual, these actions would be negligible. However, if a significant proportion of the Co-op's two million members all sign up, the amount of carbon saved from emission would be huge. This reminds me of the PledgeBank website, where people promise to perform altruistic actions only if a sufficient number of other people also perform them, such as "I will give blood but only if 3 other people will give blood for the first time." This is, of course, an illustration of the power of Co-operation; that we can do more together can we can do alone.
Here's a couple of photos from the folk festival last month. The first one shows me (on the left!) doing Co-operative type things with a particularly colourful member of the public.