Open source Alternatives to Visual Studio 2005
#develop (short for SharpDevelop) is a free IDE for C# and Visual Basic.NET projects on Microsoft's .NET platform. Features code completion, forms designer, syntax highlighting, code bookmarks and much more.
Code::Blocks is an C++ IDE which makes it easy for experienced as well as new developers to create applications. Application made with Code::Blocks and based on wxWidgets - are portable between Linux and Windows (re-compile is of course necessary). Code::Blocks can be configured to work with a number of both commercial and open source C++ compilers making it easy to get started and to build the best executable code. It also integrates with Gnu Debugger (GDB) for on-screen real-time debugging. Standard IDE features such as syntax highligthing, code folding are supported together with a tabbed interface. Furthermore Code::Blocks' functionality can be extended by plug-ins - if you have a special requirement you can even develop a new plug-in yourself and make it available to the rest of the world.
MonoDevelop is an open source free Gnome integrated development environment (IDE) for C#. Eventhough MonoDevelop has a short history it has some of the same features you would find in any professionel IDE. The features include GTK# GUI designer, all built-in documentation you could wish for, code completion and more.