The Tor network is generally useless and there's tons of planted child **** on there.
Don't visit the sites, don't buy illegal drugs from Silk Road either
unless you really understand anonymity.
The only useful onion link imo is perhaps the Info Exchange, if you like talking about engineering and so on, hacking, conspiracy stuff.
Real 'Dark Nets' aren't open like Tor ... :\ still hate that it's been mainstreamed >_>;