Getting old technology to do new things in a creative way is fun. Take, for example, Tony Kan of the My Apple Newton blog who details how he uses twittermail, to send tweets via email and Twitter's now defunct RSS feed to receive his incoming feed. Though Twitter no longer supports RSS, the link for your account is still live and kicking. Best of all, both services are available for free.
Using a combination of services is one way to tweet from your MessagePad, but there are other ways, too. Some folks use Newtscape, a text-only web browser for the MessagePad, to browse Twitter's mobile website. Others like Ron Parker use email on the Apple Newton to both send and receive tweets. It's rudimentary, but works well on the iconic Apple device.
Anyone else out there tweeting from legacy Apple hardware? If so, how do you do it?