thing 14 - Technorati
I did have a look around in Technorati. 
No doubt the website has changed somewhat since first having to do these 23 things. We had exercises to do but due to the changes the exercises did not make sense.   Had a look at tags and searched by them.  Had a look  at  a few other things.
I was not keen on Technorati and I don't think I would use again.