A friend of mine, called Tiggr, originally wrote this rather nice clock for his NeXT machine. So he deserves all the creative credit. This clock is an arc ranging from the hour-hand to the minute-hand. It is therefore always possible to "see the time" on this clock. If the shape is, say a capital C, the time would be something like 17:05.
I didn't look into Tiggr's source, but considering the differences (or lack thereof) between OpenStep and Mac OS X it is probably much like mine.
To use this module double-click it to install. If you want to install it manually simply put it in your user directory, in "~/Library/Screen Savers" or system-wide in "/Library/Screen Savers".
Then use the System Preferences... panel to select this Screen Saver.