20 Things They Don’t Want You to Know: This is just one page in an excellent article from PC World (found via Slashdot) that has links to multiple resources for finding passwords that you’ve forgotten.
Finding license keys for software you currently have installed
Revealing saved passwords in IE that you don’t remember (note that Firefox lets you display these, which is so handy sometimes)
Resetting the Windows administrator password when you don’t know it
Handy stuff. (The rest of the article is great too, especially the link to this page with the IVR codes to get a human operator at dozens of companies.)