Where do most people upload their animations?

Besides leaving it on their computer … Thunder indefinitely.

Youtube or vimeo.

Is there like a website where only Blender users upload their animations? Would be kinda cool!

I’d have to say Youtube. If ur looking to build a sort of portfolio of your progression as an artist, I think that is the best place to do it. It is familiar to just about everyone and has the largest audience. I wish there were more options for video uploading but Youtube is so big now that I doubt there ever will be any.