Google's SVG Web does this. According to the project website:
SVG Web is a JavaScript library which
provides SVG support on many browsers,
including Internet Explorer, Firefox,
and Safari. Using the library plus
native SVG support you can instantly
target ~95% of the existing installed
web base.
Whilst it's described as a JavaScript library it also requires Flash 9+. This isn't usually a problem, but if you're in a corporate environment with old Flash or no Flash on the workstations it's not going to work.
Also, it is still in Alpha which could be a problem, depending on what your project is.