Not really, not in a cross-browser manner. In Firefox, Safari, and Chrome, you can remove the default radio-button styling by setting appearance:none; (with vendor prefixes), then you can style it as you like. But IE and Opera don't support this yet.
The only reliable way to achieve styled checkboxes is to use javascript to make a different element act like a checkbox. But, of course, then you're screwing people with javascript disabled. In the end, the problem is sticky enough that I tend to leave checkboxes unstyled except for positioning.
