Type in your password at How secure is my password and see how quickly an average desktop PC could crack it. The results might surprise you. Play around by adding extra digits or different character types and you’ll soon see that a strong password is characterised by a variety of character types (upper and lower case, numbers, special characters) and most importantly by length.
I’m reliably informed that this site is not in fact harvesting passwords for malicious purposes. It’s own disclaimer says:
This site is for educational use. Due to limitations of the technology involved, its results cannot always be accurate. Your password will not be transferred over the internet.
The site is sponsored by Roboform, a free online password manager. I guess they’re hoping you’ll sign up.
This would be a great activity with students allowing them to see how easily simple passwords can be cracked and perhaps providing a competitive note to password selection.