Thanks Dickster. Before I trashed finder prefs and system prefs, I tried just emptying my trash and restarting, and that did the trick - my menubar clock is back. Looks like emptying the trash may be next most useful generic trick next to rebooting! Thanks for your help.
My OS X (10.5.6) gave me what appeared to be the blue screen of death today... mid-task it went blue, then rebooted. I noticed that the menubar clock in the top-right corner was missing, as were most of the other icons normally visible up there. I went to System Preferences/Date & Time/Clock...