This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
There are mentions of some libraries in the book though - YUI, jQuery, prototype.js, but these are more like real life examples of how a library approaches a problem, e.g. inheritance.
For quite a while I was feeling against using third-party libraries, especially for simple tasks, because you end up "paying" with a 100-200K download for a simple DOM manipulation. YUI changed my mind though, I really liked it, especially the fact that you can only include the parts of the library you need. I work at Yahoo! now so I'm probably a little biased towards YUI vs all other libraries, but I really liked YUI even before I joined Yahoo.
Thus said, jQuery is also a great library and has a nice "do more with less code" approach. Which is actually what YUI seems to be embracing too in its newest 3.0 preview release. Code such as: