With the Joomla! component TweetScheduler, you can schedule tweets ahead within your own Joomla! backend. After setting up a cronjob and your twitter-accounts, you can just start a new campaign - setup all twitter-messages - and TweetScheduler does the rest.
An essential tool when using tweets on a daily basis: Spend your time efficiently, by spending some time every week setting up your tweets and let TweetScheduler do the rest.
To schedule tweets, you will need to setup a cronjob in your hosting environment. Tweet authorization is done through OAuth. All code is GPL-ed and source code is accessible to all customers.