CSS Globe has some tips for optimizing your CSS.
While in a similar vein acomment has a list of best practices for CSS.
While I personally would like to add: comment, comment, comment, and comment some more!
And rounded corners are still all the rage and instead of sweating over them, jQuery comes to the rescue yet again with a simple, small, elegant solution. Beautiful.
So, I was playing around with my other blog today, trying to remove the focus outline that Firefox applies to focused links. Adding a {outline:none;} worked on everything except my headers. I tried drilling down the cascade, (example: h3 a:focus {outline: none;}), but it didn’t work. Frustrated, I turned to google. Lo and behold, the answer was quick, easy and awesome. Simply use the wildcard selector!
*:focus {
outline:0;
}
Chris Coyier, author of one of my favorite blogs, CSS-Tricks, posted about a project his firm created for Beacon Athletics, a specialty turf company. Using jQuery’s UI plugin, they created a cool, user friendly and memorable webpage. Go on and check it out! Now!

Chris Coyier at CSS Tricks has put together a great post which outlines exactly how to use floats. I wish that I had been able to read this when I first started out!
Check out the style switcher Komodo Media built for the Smashing Magazine contest. When you drag the slider, the amount of foilage changes! Very cool.