140 characters seems short, but managing a Twitter account can be time consuming. Especially if you're operating an account for your business, you may not be able to send messages and respond to follows 24/7. TweetLater is a service that makes tending to Twitter easy through three functions. Auto-follow adds back new followers. Auto-welcome sends a greeting to new followers. Scheduled tweets sends prewritten messages at any future time you specify. TweetLater comes out of Saint John, New Brunswick as a venture of Dewald Pretorius.
We use TweetLater for managing the Techvibes Twitter account. All functions are handled through a web interface; easy to set up and you never have to worry about it again. Auto-follow is most handy with the high volume of followers we get. When sending messages during the day, we still usually just use the web interface, but the scheduled tweets functionality is handy for the occasional off-hours message. I feel that there is huge room out there for Twitter management tools with more functionality like relevantly grouping contacts, blocking spam, and filtering messages by relevance. But for now, we're early in the game, and for what it does, TweetLater is the best.