Overleaf is described as ', formerly WriteLaTeX, is a collaborative writing and publishing system that makes the whole process of producing academic papers much quicker for both authors and publishers' and is a popular website in the News & Books category. There are more than 25 alternatives to Overleaf, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and Self-Hosted solutions. The best alternative is LyX, which is both free and Open Source. Other great sites and apps similar to Overleaf are TeXstudio (Free, Open Source), Texmaker (Free, Open Source), TeX Live (Free, Open Source) and ShareLaTeX (Free, Open Source).
iMathEQ is a mathematics equation or formula editor. It is a WYSIWYG online equation/formula editor allowing users to input, edit, print math equation or expressions. Provide interface for easy integration with web site or mobile app.
RedCrab Calculator is a mathematics software with fullscreen editor for the free placement of algebraic formulas on the worksheet in mathematical notation. Results can be displayed in different numeric formats and in diagrams. Images and texts can be inserted.
latextopdf.com Offers the capability to convert your tex file to PDF online for free. No registration, installation and email address required. It is free and safe to perform latex to pdf conversion process. Free online service for turning .tex files into PDF documents.