There was an application called "TinkerTool" that made it easy to toggle the view of invisible items in Panther (10.3.x) but since Tiger came out, I have had trouble finding one that does the same thing. "TinkerTool System" does many things but does not have an option to view hidden files.

However, it turns out the setting is an easy one to change by entering the following into the terminal:

defaults write com.apple.Finder AppleShowAllFiles 1

Then restart the Finder!

Change the 1 to 0 to turn them off again.

Or download Invisibles

Thanks to Pope Stewart for the tips.