I spend a good deal of my time working at the command line. In fact I rarely use any other graphical applications than a web browser and an editor. I've found that it's often much quicker to do the task at hand on the command line than to use an interface which was primarily designed with mouse users in mind.
rainbowstream - A smart and nice Twitter client on terminal written in Python.
Terminal-based Twitter Client with images and all...
More than just this "color to alpha", this post describes in detail useful methods and approach to ImageMagick manipulation.
cmus is a small, fast and powerful console music player for Unix-like operating systems.
define interface for your command-line app, and automatically generate parser for it.
This tool lets you simulate keyboard input and mouse activity, move and resize windows, etc.