For you Mac gurus out there, this is going to sound like child's play.  I finally took the time to figure out today how to change an icon for a particular folder (applications and files work the same way) to something other than the default.  I have a folder named 'Projects' under my Documents folder that houses the code for all the sites that I'm working on at any given time. I had added that Projects folder to my Finder sidebar but, as expected,  it was displayed with just the standard folder icon.  I found a custom one today on one of the many free icon sites out there and decided I wasn't getting up until I figured out how to make the Projects folder use that icon.

Luckily for me, there was a nice tutorial on Apple's site that showed exactly how to do it.  Basically you right click on the icon you want and choose "Get Info" then click the icon in top top left corner of that window.  Click Edit - Copy in the top bar. Then bring up the info window for the folder you want to apply the icon to, click on the same icon in that window and click Edit - Paste in the top bar and VOILA!

Simple pleasures are sometimes the best...