[Roedou]

I wrote up advice about the 'Rapportive Hack' last year, and published a spreadsheet to automate it: http://www.distilled.net/blog/miscellaneous/find-almost-anyb...

which others have taken and improved in creative ways.

This was one of my favorite versions, which checks against Gravatar: http://linksy.me/find-email

[allforJesse]

And I built a slightly more extreme version based on the original! The main difference is you can check multiple domains at once, but the most likely versions still appear early in the list instead of checking each domain as a full set in sequence:

http://metricsparrow.com/toolkit/email-permutator/

[walls]

This site is broken in Chrome and Firefox, at least.

[TomAnthony]

Works for me in Chrome (on OS X and Windows 8). However, it does sometimes seem to stop working for periods of time.