Twitter has released a mobile version of its Web site at http://m.twitter.com. Instead of sending and receiving SMS messages each time you or a friend posts a status update, you can just do it on the Twitter mobile site.
Any serious twitterer probably has an unlimited texting plan. But for those who were paying a la carte rates, this can significantly reduce the sting. It also offers a much nicer interface (read: there is one) than SMS and some additional functionality without having to memorize cryptic commands.
One pet peeve: URLs aren’t hot, so you can’t navigate tweets from Twitter GPS.