Author/photographer Ben Long has created Camera Raw Version Control, a “simple package of droplets and Automator actions [that] let you easily create and manage multiple versions of your raw images.” Since ACR edits are stored as tiny, easily portable XMP files, this method lets you create versions with almost no hit to your disk space.
Ben has been busy elsewhere as well, updating his Photoshop Automator Actions to v2.2 (offering full compatibility with Intel-based Macs as well as 2 new actions) and producing an excellent Digital Camera Buying Guide for CreativePro.com:

• Part 1: Budget, SLR vs. point-and-shoot, and resolution
• Part 2: Exposure controls (program modes, shutter speed, aperture, white balance, and ISO)
• Part 3: Light meters, lenses, image stabilization, autofocus, and flash.