In what way can the read-write Web help in a recession? You can, of course, flog all your belongings on eBay, or you can go to your favourite social networking site and have a good gripe about the state of the economy. Perhaps more usefully, there are a number of sites that facilitate pooling of resources that might be worth a look. Sites such as Liftshare and TfL's London Liftshare could help reduce the cost of running a car, as well as helping the environment a little. Instead of buying or selling services - both difficult when times are hard - maybe try exchanging or bartering skills with others, through Teamuphere or Skillsexchange (read that one carefully...), for example. Then there's the old concept of home exchange (Home Base Holidays - again, read carefully ;-) ) or Home Exchange. There are no doubt many more ways in which pooling or sharing can take place, and Web 2.0 sites are tailor-made for facilitating them.
I found these during a short Google. Disclaimer: I haven't tried any of them - but may well do so soon.
Does anyone have any other ideas and links along similar lines?