jQuery has been in existence for years. It’s nothing new, and it’s certainly not exciting. However, it’s the industry standard for DOM manipulation, and it’s under active development. Not long ago they gave some previews of jQuery 2.0. It’s nice to see it active and in constant improvement (unlike poor jQuery UI).
Data intensive applications need a lot of charting and graphing so that user’s can get better insight into their data. D3 provides a strong foundation that other libraries can be built on top of. Unfortunately, there haven’t been many quality libraries built for it, but it still provides a great feature set for building custom data visualizations.
I’ve had my eye on this one for a long time. It provides a framework for quickly building a full client-server application that allows live-collaboration. I still don’t feel like its ready for prime-time yet, but it’s a very exciting and ambitious project. Once they tighten down the security, and allow it to be scale-able, I think it will turn into a big player.
Here at Nodeable we use all of those libraries except for Meteor.js. They have been very helpful to organize a large code-base for our ajax driven web application as well as our mobile web application.