Yahoo! have released (under a BSD licence) a user interface library along with an accompanying set of design patterns. The library contains several utilities including Yahoo!'s own event handling and Ajax connection scripts. These helpers are designed to wrap up common requirements into a cross-browser solution so that developers don't need to write all of this stuff from scratch everytime. I quite like Yahoo!'s modular approach to these utilities as you can just use the parts you need rather than including one large script like prototype for example.
To accompany the UI libray Yahoo have also released a set of design patterns to describe optimal solutions to common problems. This set of guidelines is a great resource for developers to help them formalise their ideas. One of the problems within a lot of websites is where the developer has set-out to create a whole new way to do something that is an established pattern. That being said patterns like these shouldn't stop innovation but be a solid base for new ideas.
Yahoo!'s Graded Browser Philosophy (via Molly)
At the same time as bringing the Yahoo! user interface library to everyone's attention, an article by Senior Web Developer Nate Koechley was published explaining Yahoo's internal graded browser support strategy. The way it works is that Yahoo! evaluates each browser's capabilities and popularity and a grade is given to designate what level of support it can expect to receive in terms of presentation and behaviour. Their approach hinged around what Nate refers to as "Progressive Enhancement". Which is to provide as much of an experience as the users environment will allow them to.
Perhaps the most important thing about this document is that Yahoo! are openly publishing this kind of content and it's confirmation that they see web standards as being important. Hopefully there will be more of this from Yahoo! in the future and with any luck this could inspire Google to pay a little more attention to web standards.