As a developer, it's often useful to be able to view hidden files, such as the .htaccess file. Normally, OS X hides these files (they are UNIX system files and supposed to be hidden to casual view, after all).
It takes some awkward messing around with obscure configuration files in a Terminal session to let them be displayed or not in Finder.
http://www.brooksandrus.com/blog/2007/03/23/mac-os-x-show-hide-hidden-files-in-finder/
There is a shortcut keystroke to expose them temporarily in Open or Save dialog boxes (shift-command-period), but this isn't very useful when you need to see them in the Finder window.
http://www.macworld.com/article/142884/2009/09/106seehidden.html
I've discovered a very nice Dashboard widget that lets you easily switch between viewing or not viewing these files in Finder. It makes life as a developer on OS X much easier.
http://www.apple.com/downloads/dashboard/developer/hiddenfiles.html
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