I really like RequireJS. The have a build optimizer. It is pretty handy. I have not tried LabJS. It looks pretty interesting. I am looking forward to more about KnockoutJS. It seems like it would really reduce the amount of code you need to write compared to pure JQuery.
I love Erlang. As someone said it is a complete platform. It is like a programming language, middleware, system monitoring software, database all rolled into one. Plus it was originally designed to create telephone switches. Bulletproof reliability was the primary concern.