Okay, so here is pretty much where all the cool websites I've found for you are. This ought to entertain you for a while. :P More coming, I promise.
http://www.kidzeyes.com/- This site isn't exactly entertaining, but if your parents let you sign up, you could earn cash. How could you not stay entertained when you have cash?! If you're over 13 there is also teenseyes.com, which is pretty much the same thing. Don't worry about this being legit, I use this myself. Totally real.
http://www.deviantart.com/- This site is perfect for anyone and everyone who likes drawing or art. Awesome site, you can meet a lot of great people.
http://www.freerice.com/- This site is really cool, you give rice to hungry people just by answering simple questions.
