I'm not normally a reblogger, but is a "necessary share".

The VS team just released the first Web Standards Update for Visual Studio 2010 SP1 and Visual Web Developer Express 2010 SP1. The VS team have focused on bringing the HTML5 support up-to-date, adding CSS 3 support and bring more new API’s to the JavaScript intellisense. The plan is to make a release about every 3 months to keep Visual Studio updated with the changes made by W3C.

Download it here - http://visualstudiogallery.msdn.microsoft.com/a15c3ce9-f58f-42b7-8668-53f6cdc2cd83 

HTML5 Validation - Video & related tags, Audio & related tag, New input types like email, url, date etc, Drag and Drop support, Accessibility standard WAI, Accessibility standard WAI-ARIA, Microdata, Schema.org plus SEO
Browser APIs - Schema validation for GeoLocation and Local Storage
CSS3 - 2D Transforms, 3D Transforms, Animations, Background & Borders, Basic Box Model , Basic UI, Behavior, Color, Flexible Box Layout, Fonts, Generated Content for Paged Media, Hyperlink Presentation , Line, Lists, Marquee, Media Queries, Multi Column, Namespaces, Paged Media , Presentations Levels, Ruby, Selectors, Speech, Syntax, Template Layout, Text , Transitions
XBrowser - browser specific prefixes like –ms; also other vendor prefixes like –webkit and –moz .

You can read more on the webtools team blog. Visha Joshi @vishalrjoshi also wrote an excellent post detailing exactly what tags and features and such are supported in this release at http://vishaljoshi.blogspot.com/2011/06/announcing-html5-css3-support-for.html .