Chatter is a relatively new addition to Salesforce, and a lot of people are asking themselves, What do I use it for? This question has been asked before by users of Google Wave, but Chatter has the advantage over Wave in that Chatter is not bravely treading where no app has treaded before. On the contrary, Chatter is very much like other social networks, like Facebook and Twitter, where you post updates about stuff that concerns you.
Facebook is for updating friends on cool stuff you did or found and commenting on these things. Twitter is for updating anyone following you about whatever reason you gave them to follow you, be it personal accomplishments, stuff found on the internet, updates for personal projects you are working on, or re-sharing news items. Likewise, Chatter should be used for sharing updates that co-workers are interested in.
So, what are co-workers interested in? Well, your manager is interested in how you are progressing in your tasks. Your underlings are interested in any major decisions that may affect them. You fellow co-worker may be interested in a work-relevant article you found on the web. I'm sure you can think of more, but this paragraph is about what you may want to post in your Chatter home box.
This post, however, is about how to use Chatter Groups. Treating groups like traditional email lists is a good idea. Create a group for your task force, to share updates with others on the task force. Create a group for Software Engineering, where you can share information about changes to your company's style guidelines or blog posts about the discipline. Create a group for all specialists on a certain topic in your company, to allow other co-workers who know very little about it to ask a question and gain an educated response. Create a group for your entire (small) company to join, and use it to send company-wide announcements. Create a group for discussion, voting, or eliciting feedback on a certain topic, such as what to do for the next company outing.
At our company, we want to replace most email communication with Chatter posts, and it seems like it is very do-able. The only limitation that Chatter has is restrictive posts, where you can send a message to just a few co-workers. That's when you resort to email. Honestly, the only messages I have in my email inbox right now is meeting invitations from my Google Calendar and private messages from co-workers.
Chatter - great for collaborating, bad for private messages.