Michael Tapes from RawWorkflow.com has teamed up with the guys from Imagenomic (known for Noiseware) to create the very cool–and free–Instant JPEG From Raw utility. It doesn’t interpret or convert your raw image data; rather, it just pulls out the JPEG preview embedded by your camera*. It can optionally downsample these JPEGs to a lower resolution as well. Check out a quick video demo of the tool in action.
I think there are some especially interesting possibilities here with DNG. As you may know, when you edit the settings of a DNG file using Camera Raw or Lightroom, you can opt to update the embedded JPEG data as well as the settings themselves. This means, as photographer Peter Krogh likes to say, that a DNG file can serve as a “job jacket”: a container that holds your negative, your development instructions, and your print. The IJFR utility provides an immediate way to extract not just the data your camera captured, but the data as processed per your instructions.
*Worth another mention: Bridge CS4 now offers the ability to browse just embedded JPEG data, bypassing the raw processing stage to enable quick initial passes through a shoot.