Yeah, reporting it is definitely the right thing to do and would totally go well for you. /s
The Internet Watch foundation is one site. There are probably others for different countries. https://www.iwf.org.uk/
The IWF has just announced a collaboration with Google, Facebook, Twitter: http://www.bbc.co.uk/news/uk-33844124
I called the local FBI office and reported the site. I never heard anything else on the matter. To be honest, I was more worried that it was a honeypot and I wanted to make sure that if they were watching, they knew that I didn't go there on purpose.