DropScript is one of my favorite hacks. It's an application for Mac OS X which lets you create new applications from any BSD program which takes files as command line arguments. Typically, these are scripts written in sh, perl, etc.
What's new in version 0.5
Version 0.5 adds a spiffy new feature: application services. Your new drop applications now export a service which is available in the Services menu of all applications (such as Finder!) that can send a file reference to a service.
Also new, in the example scripts we now have a README. Yes, folks, a wee bit of documentation on how to write scripts for DropScript.
I'm now building and testing on Mac OS 10.2. Your mileage on 10.1.x may vary.