I love to learn, and I read constantly because I enjoy it. So a lot of what I know comes in osmotically from whatever I happen to be reading.
When I have a specific question, one of the first places I turn to is the encyclopedia. Many people are amazed by this, but I LOVE encyclopedias. I have a 1974 edition of The World Book encyclopedia (go to a used book store and you can pick up a used set of encyclopedias for next to nothing). I have not read every word of it, but I have looked at every single page. It is amazing what you can learn. I also have Encyclopedia Britannica on CD, and I love it. There's a ton of information in EB.
I have a pretty good library at home and I can look things up in those books as well.
Obviously I use the Web a lot -- that's why nearly every page on HowStuffWorks has links. I find the information I need in search engines. It's a very tedious process at times, but if you are persistent you can find the answer to maybe 80 percent of your questions using a Web search engine. I happen to favor Google and Go, but I think each person finds a search engine that "feels good" to them. I also love Yahoo!
One of my favorite places is the library. Fortunately, it's right on the way home from work and it's open late! It is unbelievable how many good books there are at the library.
Finally, we are able to talk to lots of experts, and they are incredible people to work with!
Here are four of my favorite question/answer sites on the Web. They can be very helpful, and they are also fun to browse through for the pure joy of learning!