But I really think this one is very cute. You dont have to have a special invite. And there is just SO many different pets to collect. You can level them up, battle them with other pets / enemies, capture other pets (just like pokemon, lol). You can dress up your own avatar, all sorts of neat stuff. Im still really new to the site myself, but I think its really well made, and its kept my interest thats for sure.
Here are some of the ones I have collected already to give you an idea.
People are really nice with the free-to-newbie forum section.