$fx() is a tiny, self-contained Javascript library for animating HTML elements. It doesn’t require any other library to function and [should] play well with any other libraries you are using (Prototype, JQuery, Moo tools, etc.)

$fx() allows you to alter any CSS property along a timeline, allowing animated effects to play in succession — i.e. in the order you want them to. It handles all of the headaches of timer controls and makes it easy to animate anything from simple, subtle animations to more elaborate animations.

Size:  4 kilobytes

jsAnim

jsAnim was created by Kevin Dolan, jsAnim is a JavaScript animation framework for creating high-impact and slick animation sequences for web interfaces. Crafted with standards and best practices in mind, jsAnim allows you to create stunning animation effects without sacrificing web accessibility of your web projects
Size : 25 kilobytes

Scripty 2

Scripty2 is a rewrite of the script.aculo.us library is a prerelease alpha version and not meant for production use.Scripty2 is divided into three parts, core, fx, and ui.

Glimmer

Glimmer is a framework for easily creating interactive elements on your web pages. Glimmer comes with wizards GUIs, reducing your coding requirements and guaranteeing standardization across your projects.

GX

GX, developed by Italian web developer Riccardo Degni, is a compact (10KB uncompressed animation effects library that puts strict web standards and best practices at the forefront of its development philosophy. Built on top of jQuery, but heavily influenced by MooTools development patterns, you can customize your GX download to include only the parts you need, making your scripts optimized for file size.