Oh man! We had a live-thread here a week or so back where I walked a guy through sizing his chain (it was too long). I go by derailleur position - large to large, small to small.
Afterwords - he could get all his gears for the first time. He was ecstatic! The thread was filled with live pictures as we went back and forth in very close to real-time. That thread demonstrated what this medium of communications is capable of when used for good. But never for EVIL!
<EDIT> Yay! Just ordered a Park Tool CT-4.2