Project Siena is a great tool to build apps with minimal coding. You use visuals, excel expressions, and some data to build the app really quick. You can then easily publish the app through Visual Studio to the Windows Store.
Project Siena was originally built for business applications but, you can use it for many other apps. In fact, I built an American Football Game on it called Football Superstar. You can check it out soon in the Windows Store. Back to Project Siena, you can build simple consumer apps and complicated apps with no coding except a few lines of excel expressions.
Overall, Project Siena is a powerful tool to build apps or even games with little to no coding knowledge or experience that is perfect for anybody who just needs to build an app real quick. You can check it out at: http://apps.microsoft.com/webpdp/app/5ae47651-e8f3-4e41-aab7-e19ab1b80180 and find more information at: http://www.microsoft.com/en-us/projectsiena/default.aspx.