If you’re running a beta of Firefox 4, you can install restartless add-ons written with the new Add-on SDK. In a nod to the Mozilla Add-on SDK‘s original project name, we’re now automatically tagging restartless add-ons with “Jetpack” so that the adventurous can try them out. Visit the Jetpack Tag and install (and uninstall) to your heart’s content!
One note: as the SDK is still in alpha, not all of the add-ons in this tag will work with all beta versions of Firefox 4. We expect compatibility to increase dramatically when the Release Candidates ship.