Nettuts+ has launched a new amazing website Prefixr using which you can make your CSS3 Cross-Browser Compatible in Seconds, now you can write the whole stylesheet keeping in mind just one engine/web browser(like webkit or moz) and let this website make it compatible with all other engines/web browsers by adding their respective tags. Prefixr will filter through the applicable CSS3 properties and dynamically update them.
The website is up at http://prefixr.com/. It also given an option to compress the CSS and provides API if you want to execute it directly from your text editor.
Please remember this website is still in Alpha stages and has some bugs like no support for properties like “border-top-left-radius“.