This week at Dreamforce we launched a new command-line interface tool for interacting with Force.com. With this tool you can quickly interact with the Force.com APIs, opening up powerful opportunities to script and automate tasks with Force.com. This tool is open-source and available at http://github.com/heroku/force.
You can immediately download the precompiled binaries for the force command-line interface and start using it today:
For a full review of this tool, and instructions on how you can fork the repository and add your own custom functionality, please see my post: A Command-line Interface for Force.com.