I was going through some stuff of John's and came across an old article from Mac World that explains about the various signs on the keyboard and how to use them right. It seems that most of us are using " for quotation marks, but that is wrong. This is used for inch! A quotation mark is: ” “
Graphic Designers often use the French one » « for aestaetic? reasons.

However, on a Forum like this, I don't really care which is used, but it's nice to know, in case you need it professionally.