CSS border art and other treats
Chris Hester’s 3D Border Demo 2 (via Web Graphics) is an impressive demo of just how much you can achieve with CSS borders. His Tips & Demos collection is worth browsing through as well; I particularly liked this Shadow Demo, although markup purists may be distressed by the number of nested divs. The sooner we can use the CSS3 ::outside pseudo element to achieve effects like this without the surplus divs the better.
Update: On closer inspection the additional divs aren’t nested within each other; they are individually positioned to achieve the desired effect.