Twollows is a command line tool for checking whether two Twitter users follow each other.
To use Twollows, just download the Ruby script and put it somewhere in your PATH. Call it with the desired Twitter screen names as arguments like this:
twollows.rb ev fiskeben
Twollows will then tell you who follows who.
This program is released under the MIT license. It is written by Ricco Førgaard, ricco@fiskeben.dk. Visit http://fiskeben.dk or follow me on Twitter: @fiskeben.
Due to changes in the Twitter API and me not bothering much anymore, this tool most likely doesn't work any longer.