Overleaf - The online platform for scientific writing. Overleaf is free: start writing now with one click. No sign-up required. Great on your iPad.
TeXworks - The TeXworks project is an effort to build a simple TeX front-end program (working environment)...
Archimedes - Archimedes is a LaTeX and Markdown editor designed to make mathematical writing easy.
Texmaker - Texmaker, free cross-platform latex editor
WinShell - WinShell is a free integrated development environment (IDE) for easy working with LaTeX or TeX.
LyX - LyX is a document processor.