FB Mood Manipulator
Facebook Mood Manipulator is a browser extension that lets you choose how you want to feel and filters your Facebook Feed accordingly.
It is based on Facebook's research into massive-scale emotional contagion through social networks. The linguistic analysis is done with Linguistic Inquiry Word Count (LIWC), the same system used in the Facebook study.
Aw yes, we are all freaked about about the ethics of the Facebook study. And then what? What implications does this finding have for what we might do with our technologies? What would you do with an interface to your emotions?