Poll: What javascript library do you use?

jQuery, Prototype, and MooTools. Pretty much standard in everything I design.

jQuery is the most useful lib.

I'm interested in Ext JS / Sencha and YUI but haven't tried them yet.

Briefly tried Dojo, it looks like a very solid framework that is really powerful if you spend a bit of time to learn how it works and fits together.

YUI for everything I do, but then I've also contributed code to YUI.

Where's the option for "I don't use a library?"

I use Ext JS at work (it's awesome) and jQuery for my home projects (it's also very awesome but very different than Ext JS).

I would recommend taking a look at Ext JS as it can do some pretty incredible things. For instance it features a layout manager which allows you to make web applications that look and function very much like home-computer based applications.