There are so many, the one I learned from, and liked very much, was:
Johan Gustafsson's Guide to ScriptingI have also heard that snYpir's
A Friendly Introduction to Code Snippets is very good, although I can't say from personal experience.
After gaining the basics I then suggest you look at scripts that others have done and learn how they did it. You can learn a lot from someone else.
And of course, for those problems you just can't solve, ou can always post a question on the forums. There are many helpful and brilliant people here ready to help.
Good luck with scripting, it is daunting at first, but once the basics are learned, things start falling into place.
-Pilot