The first popular IDE was probably Borland's old TurboPascal for DOS. Turbo Pascal included an editor with a WordStar command set, a compiler for Pascal code, and an integrated debugger. If your code encountered a syntax error while compiling, you were placed back in the editor, with the offending line of code highlighted.
GnuEmacs and XEmacs were originally just TextEditors , but because of their extensibility they got more and more IDE-like features. In addition they have got many additional extensions, that make them even more like an IDE.
The defacto standard IDE now is probably IBM's Eclipse IDE, written in Java and freely available under an open source license.
See the IDEFamily for a collection of IDEs