The previous two posters were pointing out the menubar clock, but I assume you mean the old floating NeXT-style (sorta) desktop clock that took up too much space and got in the way? ;-)
Sorry - it's gone for good. Personally, I don't miss it but I know a few folks who do - the best suggestion I can come up with is go check out a few shareware clock apps on MacUpdate or VersionTracker - I seem to recall seeing a few that could handle desktop clocks.
Alternatively, turn on 'developer mode' in dashboard and drag the dashboard clock (or anther clock - there are a few out there) over to your desktop (click and hold the item, then hit the dashboard hotkey again).
You can turn on dev mode by opening terminal and typing the following followed by hitting the enter key:
defaults write com.apple.dashboard devmode YES
Well if you look at that link i posted there is one which seems pretty good, simple floating clock. Doesn't behave properly with spaces yet but the guy made it because Leopard lost the clock.