A free IDE for C#, VB.NET, & Boo projects on Microsoft's .NET platform
SharpDevelop is the open-source IDE for the .NET platform. Write applications in languages including C#, VB.NET, F#, IronPython and IronRuby, as well as target rich and reach: Windows Forms or WPF, as well as ASP.NET MVC and WCF. It starts from USB drives, supports read-only projects, comes with integrated unit and performance testing tools, Git, NuGet and a lot more features that make you productive as a developer.
Easy, fast, and lightweight backup and synchronization app for Windows
Create Synchronicity is an easy, fast and powerful backup application. It synchronizes files and folders, has a neat interface, and can schedule backups to keep your data safe. Plus, it's open source, portable, multilingual, and very light (210kB).
Open Source Web Application Framework for the Microsoft ASP.NET platform.
This is Dialogic IVR, CRM, Call Center, Fax Server, Email Server etc.