Kile is an integrated LaTeX environment for the KDE environment, which in turn is available on Linux, Mac OS-X and Solaris.
TeXMaker is a cross-platform graphical shell.
Gedit LaTeX plugin.
For MS Windows, MiKTeX comes with TeXnicCenter, an integrated development environment (IDE) for developing LaTeX-documents.
The LaTEX Editor, LEd, is a free graphical environment for rapid TeX and LaTeX document development. LaTeX Editor is designed to work on MS Windows 95/98/Me/NT4/2000/XP/2003/Vista.