Uhhmmm. I'll argue that overall reddit is a huge time sink, rather than a useful site. For reddit to be worth your time, you really need to narrow down what you are looking for (by subreddit, and than further by personal topic), otherwise you'll waste lot of time looking at marginally interesting things and reading marginally interesting comments.
There seems to be a lot of knowledge that LessWrongers have which is fairly awesome, but not particularly well-covered on Less Wrong.
What other sites do people recommend?
I originally came to LW through HN, and Paul Graham was somewhat influential on my early high school thoughts.
I've poked through these a bit on recommendation from other people, and they seem ridiculously useful.
If you want to be super nice, could you link to some of your favorite posts/articles?