just a word of warning about DeskShade...
i've used it in the past to lock my desktop, and the "hacker log" is a great idea as well. 🙂
but sometimes it can jam up, very easily. i once had alot of stuff open, and then just went to test the lock desktop function, and an app popped up a window. i couldn't click it of course, but i couldn't get back to unlock the desktop either. but that was a while ago... it may be better now.
also - i just use the screensaver to lock my desktop. i use the Dim screensaver so it doesn't waste CPU time, and leave all my apps open and running while i'm away. i suppose you could also make some screensaver in Quartz Composer that doesn't even change the screen at all... that way when you activate the screensaver, it'll appear to have no visible affect on the screen... hrm... now there's an idea. 😀 i'll have to get fiddling on that one...