PlotLab is a set of .NET 2.0-4.0 components for very easy and fast Data Visualization. Allows very fast display in a Plot/Scope/Chart or Waterfall form. Great for FFT Visualization! Free for non-commercial use.
Downloads: 113792 - Shareware - Download Now

This is a free sample add-in (ready to install and use) that adds some useful features to Microsoft Excel. It contains a full source code in VB and C# and supports Excel 2003 and 2007. The add-in works in VSTO 2005 SE and VSTO 2008 (VB.NET, C#).
Downloads: 94366 - Freeware - Download Now

A fast, portable, simple, and free IDE for C/C++ programming on Windows. It uses Mingw port of GCC (GNU Compiler Collection) as it`s compiler. Embarcadero Dev-C++ can also be used in combination with Cygwin or any other GCC based compiler.
Downloads: 28631 - Freeware - Download Now