As promised, Clippings is now compatible with Portable Firefox 4. Follow the download link in the Clippings installation page to download it to your Portable Firefox browser.
About Clippings Portable Edition
This special release of Clippings is intended for Portable Firefox users. The difference is that the common clippings feature is disabled; the Clippings data is stored in your Portable Firefox profile directory -- typically on your USB flash drive or other portable media in which Portable Firefox is installed. This ensures that your Clippings data stays in your portable media.
Clippings Portable Edition can also be used with Portable Thunderbird. Simply use the same download link as given above.