Introductions: Basic places to start on the .onion network.
 
ion's Hidden Wiki (Traditional wiki after Matt's went down) - User edited. Has lots of links and pages. It's been down for a good 2 months now but I'll include it if it ever comes back up: http://kpvz7ki2v5agwt35.onion/wiki/index.php/Main_Page
Censored Wiki - A censored Hidden Wiki mirror with better uptime. Hosted by TriPh0rce: http://3suaolltfj2xjksb.onion/hiddenwiki/
Hackbloc's Hidden Wiki Mirror - User edited mirror. Best alternative to the original Wiki as far as pages go: http://xqz3u5drneuzhaeo.onion/users/hackbloc/index.php/Mirror/kpvz7ki2v5agwt35.onion/Main_Page
Hidden Wiki Mirror - Heavily outdated. Use if you have to: http://7jguhsfwruviatqe.onion/index.php/Main_Page
Core.onion - The long-standing introduction place for Tor: http://eqt5g4fuenphqinx.onion/
TORDIR - User-submitted links: http://dppmfxaacucguzpc.onion/
Sites Deep Web - Uncategorized list of links: http://ekwreugkil5ncyyh.onion/
Torlinks - Fast, moderated, and up-to-date without censorship. Essentially a mirror of THW but not in the Wiki format: http://torlinkbgs6aabns.onion/index.php
CircleServices - Domain hosted by mixie. Contains a lot of basic tools you'll find, like file hosting and a PM service: http://4eiruntyxxbgfv7o.onion/