Right off the bat, let me say that there is not a way to recover a password (without some actual cracking/hacking which I don't know how to do). Resetting your password is your best bet.
So the first step will be to determine if you have any way to log in to the RPi.
If you're able to log in with a user that has 'sudo' rights (this includes SSH... perhaps you have keys set up properly but forget the actual user password, which I ran in to), simply typing:
sudo pwd
should prompt you to create a new password (without having to enter your current password).
Another option would be to run the starting config and change the password that way.
sudo raspi-config
If you're completely locked out, you can try the technique mentioned here (http://www.raspberrypi.org/phpBB3//viewtopic.php?f=47&t=20397), though I didn't have any success with the strategy. It just kept me from finishing booting up the RPi.
I haven't found any good techniques to enable root access period (putting the conversation of why you'd even want to do that aside :) ), let alone if you can't log in. Somebody can correct me if I'm wrong.
Hopefully this will save you from blowing away an image with a fresh one. If this saves one person, figure it's worth the time to post :)