A lot of Web 2.0 sites have rounded corners on everything. This is can be done with background images, but this leads to bulky webpages and areas on your web page that can be difficult to resize or change the colors.
This website demonstrates how to get rounded corners with only CSS and a downloadable javascript file. Pretty cool stuff! This is a great way to jazz up your website with only a little effort.
2/2/07 Update - I spent a couple of hours working with this code yesterday. It does some cool things, but it's not a magic bullet. It doesn't always knew what color to use as a replacement. And, if you have two rounded corners that are too close together, it does some funky things. I tried to round the corners of a div closely next within another div to create a rounded border effect and this is what I got:
