This is from the folks at buffer who did some research into viral headlines.

Read more about it here – a scientific guide to writing great headlines
http://blog.bufferapp.com/a-scientific-guide-to-writing-great-headlines-on-twitter-facebook-and-your-blog

See the full list
https://docs.google.com/spreadsheet/ccc?key=0AhO_gyaQUNXUdDNLZ2twZ0tLVEFDVEVSN0ExaUVMbGc&usp=sharing#gid=8