Are there other websites like this?
There are really no other sites like this. There is another great forum site called Wordreference but those guys do NOT mess around. They know that everything you post is archived for posterity so that anyone that searches may come up to your post to find the definative answer. They are very serious over there, although thier answers are top notch and they are a great bunch of guys. I was a serious member when I was learning Japanese and it wasn't "fun" per se although you did learn. Try out livemocha.com if you want another fun site like this (no forum there though).
I have tried other sites before, but nothing is as enjoyable and entertaining, as friendly and alive, as in-touch-with-reality, and yes, definitely, as organized as this one. More than that, incredibly it's all for free!!! It's like finding your soulmate, if you believe in such a thing.
Probably, but they sure wouldn't be as much fun, as eductional and as well organised. And they would probably charge you more than you would be willing to pay.