I do exactly this. I use oysttyer[0] to do the tweeting, and I wrote a bash script to:
* read a line from a file;
* tweet that line;
* rotate the line to the bottom.
Then I run that script from a cron job.
The magic is in oysttyer. It is a little tricky getting it to run automatically because it requires the tweet text as a command line parameter, and can't read it from a file or stdin. Even so, all pretty trivial, really, depending on your existing skill set. You need skills to:
* read the line and feed it to oysttyer;
* rotate the top line to the bottom;
* set up cron scheduling.
[0]
https://github.com/oysttyer/oysttyer