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?