http://www.community-intelligence.com/blogs/public/
This link discusses so many categories of collective intelligence. You should check it out, its filled with information.
Collective Intelligence is obviously a collaborative process. Lets use wordpress.com for an example. You find a topic of your choice, write about it, someone responds to your writing and writes a blog based on what they learned from you and mention your link. Friends of the “responder” check out the link and also respond. This is a community beginning to evolve. From there, there are more than three people who are all into the topic and from there they can share and contribute ideas. After they all write blogs, more people begin to follow the links that all go back to the first blogger. Everyone is now collecting the information they have retrieved and now sharing it amongst each other.
good example. word press is very much collective intelligence, as are google, facebook, yahoo, and most search engines. Colletive intelligence is based on the fact of people sharing what they know in a useful shape form or fashion.
I think forums are 1 of the best areas of collective intelligence!