Less Wrong is a multi-user blog focused on the refinement of human rationality. Originally started in 2008 by Eliezer Yudkowsky as a way to express some of his thoughts on rationality and get feed back the site has grown to include the writings of several members and cover a pretty wide array of topics such as ethics and metaethics, decision theory, linguistics and semiotics, reductionism in everyday life, neurology and psychology, and of course rationality. I think it's easy to assume rationality is simply making sense or not doing stupid things or following some set of rules and for some people it is but it can be so much more.
If the topic of rationality or just thinking better in general interests you then I'd suggest visiting the site. While I consider Less Wrong to be mostly transparent and understandable it has portions that are pretty jargon heavy. The following posts are good starting points:
What Cost for Irrationality?
A Fable of Science and Politics
Guessing the Teacher's Password
What I've learned from Less Wrong
Hindsight Devalues Science
RUST IS FOR THE WEAK