|Tor is not for Everyone...|
A lot of it was stuff about encryption and one guy had written an enormous essay about the Matrix, but there was some horrid stuff too. The most disturbing things found were articles on how to kidnap children and various child pornography entries about specific kids, which were described in graphic detail. It's the most f**ked up stuff I've ever read and it is the unfortunate side effect of a truly anonymous network. You can easily avoid those pages by just looking at the index and clicking on the links that aren't about CP, since there's also some perfectly benign stuff on there too.
Tor doesn't have a search engine, so many .onion sites probably can't be accessed unless you have a direct link. Outside of the Hidden Wiki it's actually pretty boring except for the fact that you can buy pretty much anything on Silk Road. Overall it's probably worth checking out once if you're curious. Be prepared for eternal loading times. Avoid anything that says "Torpedo" or "hard candy", disable images and scripts, don't be stupid and you should be fine.