I’m relatively new to Mac OS X and have been struggling to find out how to quickly “Show the Desktop” to see all the icons I have in there.
I have been used to clicking that little “Show Desktop” icon on the bottom left of the screen in Windows and was looking for an equivalent on my Mac.
Fortunately, there is! But it’s not an icon that you would click but some keyboard shortcuts you need to type. For me pressing fn F10 did the trick.
You can find more Expose tips on this page.

Check this out: http://www.everydaysoftware.net/showdesktop/
On my 2008 MacBook:
F3 = Expose
F4 = Dashboard
F5 = blank, so I set it to activate – Spaces
F6 = blank, so I set it to – Show Desktop
this way you don’t need to press – fn
Hope this helps.
Thanks Jude for the tip! That sounds easier indeed.
Control-2 works on an Autumn 2009 MBP on 10.6.4
Correction. Control-2, just switches to the 2nd Space. If that space is displaying the desktop then the functionality is almost similar. One can also use Control-Arrow.
Another way of showing the desktop that is more similar to Windows, is to right click the Finder icon on the dock, clicking Option and selecting Hide Others. This will clear any open Windows except the Finder.