Logic!

I got pointed to Fallacies and their causes by walkingbear

It looks to be very useful.

(edited:)

Several more:

Fallacy Tutorial Pro 3.0
Stephen's Guide to the Logical Fallacies
\How to argue

Feds nix antigay protection

Gay gov't employees lose their protection

For my friends who do tech support or customer support

Check the last couple of strips at Queen of Wands

A friend who works at comcast wonders if the artist works there too. :-)