The "Did you mean" feature

[lucym]

Hello, I want to add the 'did you mean' feature (like on Google) on my shareware site, where a lot of users have mistypes, and they get 0 results... so they exit the site very fast. Do you have any idea how I could implement such a thing? Does it require a dictionary or something? I found some scripts, but none of them gave relevant results... just stupid, irrelevant suggestions. Any help would be appreciated...
Code samples would be jus great
Thanks, Lucy