TurboWidgets: the Dojo ecosystem
TurboWidgets is a set of nicely featured widgets for Dojo toolkit (especially the TurboGrid). They're not opensource, but free for non-commercial use.
It's interesting to see how the architecture of Dojo widgets, which is highly extensible, allows the emergence of a very diverse and healthy ecosystem around the toolkit. The TurboAjax Group is building commercial extensions, Jot and a number of web 2.0 companies use it to build their offering, and a lot of open source projects have chosen Dojo as their preferred Ajax library (including Cocoon very soon).