This website has a lot of colouring pages. It started small but we have now over 2000 coloroing pages that we offer for free. The website has a 1000 unique vistors a day and is quite a success.
In the backend there are statistics and a way to add new coloring pages. The website has also a great tool so you can color online. Which is still under development. Soon we will release an app in the app store so you can draw coloring pages online.
Please take a look at coloringpage.ca