password recovery?

Hi there,

I am looking to implement a password recovery feature so users on my site can request a password when they forget theirs...

My passwords are one way encrypted, using a sha1 hexdigest so currently users would only see a garbled string which is not their password.

So - are there any tutorials that cover this as a walkthrough, so I can learn as I go? I've tried google, but there's so many suggestions, it's knowing which is the best etc... Also couldn't see anything that covered that on Railscasts.com

Any ideas?