The calendar on the clock shows up on the tasklist and has a silly title, and it needs to be sticky.
I hacked on this a bit but gtk_window_stick() doesn't seem to be working for some reason. Needs debugging.
It seems to be working for me. Strangely enough, it gets a flicker of focus when changing workspaces -- perhaps a metacity bug. The only other feature I can think of is to always keep the current day highlighted.
Scratch that. GtkCalendar is a POS -- I don't see any nice way to fix the selection problem w/o touching GTK+. The flicker of focus seems to be metacity giving focus to the calendar upon changing desktops, and then noticing the mouse is over another window and giving focus to that window. If that's a bug, I can open it in metacity.