http://homestudy.ihea.com/contents.htm

I went through this material as part of getting a hunter safety card before I bought my AR.

The 'Modern Firearms', 'Ammunition', 'Firearm Safety', and 'Shooting Skills' topics are a decent basic intro for someone new to guns.
It's no substitute for hands on training with someone experienced, but certainly worth considering as a supplement to hands on training.
-2C