[An earlier version of this was accidentally mis-posted to my "world" blog.]
I think TUAW pointed me to Dockables. These are donation ware applescripts with a full installer and excellent icons. I have "sleep", "screen saver", "screen capture", "screen sleep" and "log off" in my Dock now. Since I don't use my Dock for much these are great to have, and of course LaunchBar (love it) can activate any of them easily.
I've always had trouble remembering the key combination for screen captures, and I don't like the TIFF format Grab uses (though I'm sure there's a way to change Grab to use PNG, I don't like those tweaks if I can avoid them). Now I use dockables, open the PNG in Preview, select, copy and then either pastse into a document or "create new from clipboard", then save with a useful name or paste. Ok, so it's not ultra efficient, but it works rather quickly.
Screen sleep is another of my favorites. It simply puts the display to sleep. I didn't think this was possible on an iMac, but it works. I can now quickly rest my screen at night while allowing backups to proceed normally.
These are also handy for the docks of my family members, who really don't know any key shortcuts or hot corner mouse actions.
I'm sending the author a donation.