I hadn't heard of about half of these - it's great that there's a sort of directory for them.
Sweet.js is pretty awesome (I was going to say it's sweet, but that's stupid). Broadway.js and Shumway look pretty awesome, I'm going to check them out tonight.
Regarding Parallel JavaScript, does anyone know how this relates to Khronos' WebCL project? Hardware manufacturers seem really interested in WebCL, but software developers aren't.