I bought this app a few days ago and it rocks big time. For a measly $5 it is virtually free. Go to http://mypostbutler.com and snap it up. It handles multiple twitter accounts, auto follow based on keywords, unfollow and bulk direct messaging to your follow list. I only wish there was an affiliate program for it, but there's not. The guy is happy making a few bucks a sale.
The guy that owned the software has sold the source code to a developer. Shame coz it was (still is) a great little tool - I still use it every day.