ICEOWS ("Interface de Compression Ergonomique pour windOWS") is Raphaël and Béatrice Mouniera's free (as in "freeware" and not as in "Wildebeste") Windows program for manipulating compressed and archive formats (.ZIP, .ARJ, .ARC, .gz, .tar, and the like). It supports the common formats natively, except for ARJ, which requires an external program to be used.
As such, it is very similar to WinZip. Except in everything that regards user interface.
ICEOWS has no interface.
Well, almost. It behaves as some weird Explorer add-in. You can open any archive, exactly as you would open a directory. Upon doing so, you get your usual Explorer window, only looking inside the archive. So you don't need to learn any new commands! For instance, you can drag and drop (or cut and paste, if you prefer) files from or into the archive. It's exactly the same interface paradigm as moving files between directories.
Sometimes it doesn't work. For instance, you cannot run an executable from within an archive, you have to check it out first. This is hardly the fault of ICEOWS -- it's an understandable limitation of the Operating System -- but the breakage of the interface metaphors can be very disconcerting. Of course, you could argue that this shows just how natural it all appears to the user.
For completeness, ICEOWS also adds entries to the standard Explorer context menus ("right click menus"), to allow you to add existing files to an archive, transform an archive into a real directory, and the like. The originality of the interface here is of course much less.
ICEOWS deserves to be tried out, if only for the sheer brilliance of its (un-)interface. Such an interface probably could never exist in a commercial product: transparency to this degree is never a good idea as regards branding and the like. Get your copy from