IIS Express

Microsoft have been working on a new flavor of IIS 7.x that is optimized for developer scenarios that we are calling “IIS Express”. It combines the ease of use of the ASP.NET Web Server with the full power of IIS. Specifically:

• It’s lightweight and easy to install (less than 10Mb download and a super quick install)
• It does not require an administrator account to run/debug applications from Visual Studio
• It enables a full web-server feature set – including SSL, URL Rewrite, Media Support, and all other IIS 7.x modules
• It supports and enables the same extensibility model and web.config file settings that IIS 7.x support
• It can be installed side-by-side with the full IIS web server as well as the ASP.NET Development Server (they do not conflict at all)
• It works on Windows XP and higher operating systems – giving you a full IIS 7.x developer feature-set on all OS platforms

IIS Express (like the ASP.NET Development Server) can be quickly launched to run a site from a directory on disk.

Look at scott Guthrie's post for more information.

Note: Beta will be released soon.