How do I access the 1/4 key?

Apple menu -> System Preferences -> Language and Text or Keyboard lets you enable the character viewer virtual keyboard. With it, you can see what Option, command-option-, command-shift-option, or control-option keystrokes will yield unusual characters, and see which font is required for specific look of those characters. I'm not in front of my 10.6 machine, but that's what I'd look at.