I’m not surprised to see more and more “lightweight” JavaScript libraries pop up as jQuery has grown in size. The pendulum tends to swing hard from one direction to the other with these things.
One that I came across recently is Minified.js:
Minified.js is a client-side JavaScript library, comparable to jQuery and MooTools in scope. Its features include DOM manipulation, animation, events, cookies and HTTP requests.
The size of the JavaScript file you send across the wire is certainly one factor to consider, especially for mobile users. I’m more curious to see what the performance looks like when using similar features. In some cases that is even more important than the size of the file.