Yes, CSS3 can create circles and ovals. Both the circle and oval on this page were created with CSS3.
The circles will render in most modern browsers. However, Opera is currently rendering the oval as a rectangle (go figure).
Hover over the oval. Remeber this site is built for modern browsers.
Join us at the CSS3 Revealed Seminar and we'll show you how to do this and more.
(transparency new in CSS3)
(vertical text compliments of CSS3)