I've noticed an explosion of Chambers using Twitter recently. There are at least 300 chambers and their staff that I know of using Twitter. Some are doing a great job and others are just getting their feet wet.
Note that the Batesville AR Chamber Exec resigned recently over an anti-Obama tweet (or more than one) on the Chamber's Twitter account. Here's the story.
I love that Chambers are using Twitter and other social media to engage their members and communities, but remember that your posts are public and can/will be found by lots of people. There have been several other examples recently of people getting fired or losing job offers based on their Tweets. Yes, you should use Twitter to promote your Chamber's events, blogs posts, positions on issues and to have conversations with your followers about all of those items. Know, though, that you can "cross a line" that offends your supporters, as seen in the Batesville example.
Check out this post of mine for some examples of chambers that are using Twitter well and some other Twitter resources for Chambers.
Also, a local business program here in Indiana recently published some great tips and advice for businesses just starting to use Twitter.
I hope you find this information helpful!

Posted by: Liz, IACCE President on Friday, March 20, 2009
This is so true. Be careful what you post on your public profile professionally and your personal profiles. This goes even more for twitter today! Chamber executives are public 24/7 already in their community and this is just another level to show they are ALWAYS representing the chamber and community... even on their personal profiles, blogs, twitters, etc. If you wouldn't say something in a stadium in front of thousands of people... don't EVER say it online!
Posted by: rburns@rogerslowell.com, jspringer@rogerslowell.co on Saturday, March 21, 2009
Good post from Curt Moss at WebLink on using Twitter etc. with caution...