Here. The Alladyn library unifies the various browser Document Object Models (DOMs) into a single object model, leting you write one set of JScript code for your dynamic sites and have it work across browsers. The library let you program Flash-like sites that don't use Flash. The gallery demos how much you can do.
It's hard to tell from the site, but it seems to support IE4+, NS4+, Opera and Mozilla. And it does all this in 2403 bytes! Truly amazing.