In April of 2008, only about 18% of small businesses even read blogs for business purposes. But by March of 2009, that figure had jumped to 40%. Remember, that's reading blogs, not writing them.
Nevertheless, David Mihm at Search Engine Land's Small Is Beautiful column advises small businesses that even if you're not ready to start Tweeting, now is the time to claim your Twitter user name.
And if you are ready to Tweet, Mihm says Twitter is good for networking, market research, lead generation, customer service and reputation management, taking orders, filling last-minute inventory, community activism, and improving your search rankings.