Microsoft have just released Project Siena, which looks like Microsoft's first big push to encourage app development for Windows 8 and RT.
Siena is targeted at “business experts, business analysts, consultants and other app imagineers”, to create apps that work “well with corporate and web data and media content: SharePoint lists, Excel and Azure tables, RSS feeds and the gamut of RESTful services”.
Siena uses the modern user interface that has become the new hallmark of Windows 8. It allows developers whether completely new to the programming world or the more experienced developer to create HTML5 and JavaScript apps.photos, videos, pen and voice notes.
Siena is currently in its beta phase, and can be downloaded for free from the Windows app store.