Check out the Rationality: A to Z contents page, click on things that look interesting, it'll mostly work out.
A Human's Guide to Words is really good exposition of philosophy. The subsequence of thinking about morality that I can point at with the post fake fake utility functions is good too. Or if you just want to learn what this rationality stuff is about, read the early posts about biases and read Knowing about biases can hurt people. That one's important - the point of knowing about biases is to see them in yourself.
I just don't know what suits you, is all.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.