If you have a message that needs to go out at a specific time in the future and can’t be there to send it out, having the ability to schedule it ahead of time is a lifesaver. Most platforms are built around the concept of real-time messaging, but a few third-party developers have created solutions that make future posting a cinch.

• EasyTweets – Easy Twitter Marketing (paid service)
• FutureTweets – Schedule tweets in the future; supports recurring events
• TweetLater – Schedule up to 12 tweets per hour or space them over time | link
• Twuffer – Schedule tweets into the future with hour increments | link