Frameworks for what?
If for RIA, the Qooxdoo, ExtJs (although there's a slight problem with the localization, the localization framework holds, but the location of its string constants out of the box not working, as far as I know, but it's solved)
The coolest Dojo Toolkit. It is divided into 3 parts — Dojo, Dijit, Dojox.
In the Dojo the most basic of features, different UI in Dijit, and Dojox experimental capabilities.
There's something just not... MD5, Base64, modules, colors, Google Analytics, security modules (dojox.security), which may, for example, to forbid to change any DOM element or to make a sandbox... Different mathematical...
There is the module dojo.gfx (or dojox, do not remember) that cross-browser allows you to draw. As HTML5Canvas only cross-browser. Using Flash, Silverlight, Java, VML, SVG, Canvas... the same Works even in IE6.
And gfx3d module based on it also allows cross-browser to draw 3D.
In General, a very cool framework.