I have recently developed a CSS3 selector engine for JavaScript called Quicksand. The primary reason was I wanted one to plug into my JavaScript library, and I needed it to be licence free. It was also a bit of an intellectual exercise, and it was fun and challenging to work on.

If anyone has a need for a CSS3 selector engine for JavaScript, feel free to use it. It's fast, light-weight, and cross-browser.

Basically what it does is select elements with a CSS3 selector (like querySelectorAll in some modern browsers). Unlike querySelectorAll, however, it will work on all browsers, supports almost all of the CSS3 selector spec (pseudo-elements are not supported as they really can't be by a JavaScript implementation). It also supports some common additions to the CSS3 standard (like the :contains pseudo-class and the != and !~= operators for attributes), and I have plans to add some more pseudo-classes in the future.