A while back I discovered a service called TweetLater. It lets you schedule and send a twitter message at a later time, when you might not be able to do so. I use it for reminders, and to send notifications out about the SquawkBox. I literally cue up two or three tweets for the SquawkBox in the morning, and then have them go out as reminders part way through each morning. Delayed twitter messages are a great marketing tool.
Here are three services you can use for this purpose:
TweetLater lets you send out twitter messages on schedule, and also includes the ability to automate reciprocal follows. If you follow me, TweetLater will automatically make me follow you.
Twittertise has the scheduled twitter capability, plus it incorporates a tracking mechanism on links included in the message. If I send a message to my followers which says “Click here to join the SquawkBox: http://bit.ly/3P3EeC”, I can later go back and determine how many people clicked through.
Easytweets (coming soon) lets you send time delayed tweets, and manage multiple twitter accounts at once.