How to detect a typo in a product search and suggest possible corrections?

Question

Given a very large database of product names, how would you detect possible typos in user searches and suggest possible corrections (Kinda like the way Google presents them)?

Answer 1

I'm sure I read that google keeps a list of what a user retypes when they get no results. You could keep a mapping of these values (say if the retyped string begins with the same letter).