https://haveibeenpwned.com/
Well worth a look.
later - if anyone is worried they might be harvesting addresses etc., I got this reply on another site:
Thank you for sharing this site with the group. I just want to confirm that it itself is not a malicious site set up to harvest e-mail addresses and other data. It was mentioned in one of the SANS courses I took for work. (SANS bills itself as "The most trusted source for information security training, certification, and research," and it does live up to its billing.)
https://www.sans.org
It's also recced here
http://www.zdnet.com/article/how-to-find-out-if-your-password-has-been-stolen/