At someone’s request I have set up an example demonstrating event based animations in DHTML. The "Toolkit" code is extracted from a Thirteenth Parallel project that never got completed, as such it is not all that stream lined or complete; however this example should illustrate a neat and quick way for developing complex animations.
To put the example into context: you could use an animation object and a 5-dimensional curve to animate an expanding panel while changing it’s colour (2d for the element’s y-position and height; 3d for the red, green and blue components of it’s colour). Also, because the animation object is not tied directly to any element or property, the on-animate event handlers could be used to animate anything from colours, widths and element positions, to frame sizes and window positions.