We’ve got release candidate bits that are close to final for Lightning 0.1 (a Mozilla calendar embedding for Thunderbird 1.5), and we’re looking for help shaking out any final showstoppers.
Check out Calendar:Lightning:0.1:Release Notes – wiki.mozilla.org for details and download instructions.
Lightning 0.1RC1 identifies itself as 0.1, but has a build ID of 20060307xx for some values of xx. The build ID is visible from the extension manager. Chances are good that there will be at least one more release candidate before we declare ourselves done.