I had once had the wmSun plugin for WindowMaker swallowed in one of my panels, but I'm using GKrellM for that sort of thing now. (My window manager of choice, for those who might be curious, is FVWM.)
So the obvious thing to do was spend an evening hacking “C” instead of “XSL” (ya gotta use your skills or you lose 'em) and port that sucker. That was the obvious thing, right?
This plugin displays the local sun rise and sun set times.
Version 0.2 has an improved solar image and more readable digits.