I posted on the other thread that I was around, but I guess I should introduce myself.
I guess the weirdest thing about me (relative to the community) is my age -- I'm still in high school and have been lurking LW since its creation and OB before that...
I'm in the Montgomery Blair Magnet program, which has pretty thoroughly taught me that I'm by no means especially smart.
I got interested in the whole rationality thing after reading some of the articles that were tangentially related to the more philosophical articles that I was interested in* and found on Hacker News. The metaethics sequence seemed much less forced than a lot of the other considerations of morality that I had heard (mostly from a Christian background), which only piqued my interest further.
Short note: Harry Potter and the Methods of Rationality is pretty much the best introduction to rationalist topics for people my age that I've ever seen, I recommended it to a few friends, one of whom started reading it, lurking LW, and convincing others to read as well.
The article most tangibly helpful in my life was http://lesswrong.com/lw/i0/are_your_enemies_innately_evil , mainly in that it helped me realize that everyone seems reasonable to themselves and that you don't get anywhere when you argue as if they're totally wrong. It's helped a lot in resolving interpersonal issues, and is probably one of the major factors of my being elected President of my school's FIRST robotics team.
*My interest in philosophy started about 3 years ago, mostly as a result of my freshman physics class and reading Godel Escher Bach.
"Are your enemies innately evil" is one of my all-time favourite posts too. I now think politics is the single biggest source of rationality failures out there (way bigger than religion).
You can find loads of otherwise really good skeptics out there who have a political view (which is fine) that they seem to think is as perfect, scientific and objective as Maxwell's equations (not fine). Politics is epistemically dangerous.