- Sharepoint Manager developd by Carsten Keutmann from here. It gives you a visual perspective to the object model of Sharepoint allowing you to explore what properties are avaialble, hwo a site is structured and load of other stuff too. There are three versions available depending on your installation 2007, 2010 and 2013.
- .NET Reflextor from here. This tool allows you to see the source code of .NET code (i.e. SharePoint itself). You load up Windows.Sharepoint.dll and you can see all sorts of stuff inside that file.
- WSPBuilder and Visual Studio Extensions for WSPBuilder from here. This tool allows you to build your SharePoint solution as a feature and takes out loads of otherwise painful manual work in achieving this goal.