and if you want to see an example for Tor hidden services that is not just another web server with dubious or almost useless content then you should have a look at torchat.googlecode.com...
This is an instant messenger that has no central server, instead each user is reachable under his .onion address. You don't have to sign up with
anybody or agree to some TOS or anything, you just start the program (which will upon first start generate a random ID for you) and you are
immediately reachable to all other users under this ID.
Each user on your buddy list will connect each other "directly" through their hidden service ID, not through some provider's chat servers, and all
messages and file transfers will travel through this DarkNet of Tor nodes while being encrypted all the time. Nobody sniffing the network traffic at
any point would be able to tell what and with whom you are chatting or where they are located, You can easily contact somebody through his TorChat ID
and talk to him but it would be incredibly complicated and expensive to reliably trace his location. TorChat is probably one of the closest to a real
private (offline meeting in the woods) conversation you can get via the internet today.