Microsoft is pushing the use of HTML5 and CSS3 more than ever. They have just released an online testing plateform to help you support Internet Explorer: modern.IE
A new set of tools to help you support modern and older versions of Internet Explorer
Additionally, you can download virtual machines with IE 6 to 10 installed for local testing or there's a 3 month trial offer to BrowserStack.
This service is very encouraging as it shows more than ever that we are all rowing in the same direction.