Adobe Bridge is designed to be highly extensible–first via JavaScript and HTML, and now (in CS3) via Flash/Flex SWF files.  SWFs can function as panels inside Bridge, letting developers write network-aware modules that can leverage the full power of Bridge (previewing images, reading/writing metadata, etc.).  Bridge PM Gunar Penikis has posted a useful example of a SWF extending Bridge:

Once loaded into the Bridge startup scripts folder, the BridgeExportToJPEG extension will demonstrate a Flash UI panel in Bridge (screenshot) that is functional in driving Bridge to create JPEGs and manipulate XMP metadata. All the thumbnails that are created in Bridge are JPEG based, so it is possible to export these thumbnails as JPEGs — for example if you want to create a JPEG catalog, or quickly send JPEGs of your RAW files.

To install this extension in Bridge, download it, then launch Bridge, go into Preferences, choose Startup Scripts, and then press Reveal to pop the folder open in your Finder/Explorer.  Then drag the script & SWF into that folder & relaunch Bridge.  It’ll then be possible to show the panel by choosing Window->Show Export to JPEG.

Granted, the interface is "engineer art" (less polished than what you’d generally find in an Adobe app), and it’s possible you’ll run into bugs/limitations.  Even so, we think the component offers some useful functionality, as well as source code you can modify as you’d like.  Thanks to Bridge team member David Franzen for whipping it up.

For more info on extending Bridge, check out the Bridge SDK.  For more examples of Flash extending Bridge, stay tuned.