Gmail

[Ilarian]

Not only does Google provide an e-mailing service such as Gmail, they are sort of becoming a community by offering Google Groups where people all over the world can discuss about certain topics or a common interest. Google also provides an IM client and a bunch of other things that require a Google Account (free) so that you can participate in whatever they have growing on their site. It's a bit cool when you think about it. For anyone interested in learning more about the services here are some links:

Google Search - Froogle - Blogger - Gmail - Groups - Talk