Via Plasticbag:

Yahoo have massively extended the already pretty terrifyingly impressive Yahoo! Developer Network with a whole foray into design patterns and client-side technologies.

So first you’ve got the Design Pattern Library, with information about mostly pretty reasonable techniques for handling ratings and reviews, navigation, breadcrumbs and the like.

Then you’ve got the User Interface Library full of useful JavaScript components for drag-and-drop, sliders and tree views, the Graded Browser Support Guidelines and the Yahoo! User Interface blog which will feature, “News and Articles about Designing and Developing with Yahoo! Libraries”.

Where appropriate it’s all been released under pretty reasonable (some might say excessively reasonable) licenses. I’d really recommend that people check this stuff out – YDN are one of the parts of Yahoo that regularly get me excited.