If the open source model has a sweet spot, it's in programming tools. Even in the deepest corners of proprietary stacks, open source tools can be found, often dominating. The reason is clear: Open source licenses are designed to let users revise, fix, and extend their code. The barber or cop may not be familiar enough with code to contribute, but programmers sure know how to fiddle with their tools. The result is a fertile ecology fed by the enthusiasm of developers who know how to "scratch an itch." Here is a very unscientific survey of worthwhile open source tools that have caught our eye. Most are relatively new; others continue to surprise us as they morph to support the latest programming trends.