Dev-C++
Dev-C++ is an advanced, freely distributed integrated development environment for Windows, created by Bloodshed Software. It is based on the MinGW implementation of GCC. Perhaps the greatest feature of Dev-C++ for OSDev purposes is that it can be used with the Cygwin toolset as well as (or instead of) the MinGW one. Read the manual to find out how.
A similar IDE, Dev-Pascal, is available, and works with either Free Pascal and GNU Pascal.
Unfortunately, the last update to Dev-C++ was made in 2005.