Q: "How can I play with the Chatter API?"

A: Two steps, five minutes!

1) If you don't already have one, get a free Developer Edition instance of Salesforce by navigating to http://developerforce.com, then clicking on "Get a Free Developer Edition" and filling out the form.

2) Install a free Appexchange app into your DE org for open source code to get you started. Some recommendations:

--http://tinyurl.com/ChatterBlacklist blocks naughty words in Chatter posts and comments

--http://tinyurl.com/ChatterInfluence shows leaderboards of who's using Chatter and how much