http://ysshlyesehcnscptskrpai4iupxccuvfcpbxk37kclbs3rsaqmolzaid.onion/darknets.html
Although, if you don't intend to do something serious, it's probably fine. Whatever? :P I2P is about as old as Tor, but much less known. I2Ps main difference from Tor is that Everyone participates with relaying traffic (participate as relays in their peers tunnels) in I2P, while Tor only a subset of the computers are relaying traffic, and acting as exit-nodes.