file - file is a standard Unix program for recognizing the type of data contained in a computer file using...
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
TrID - Allows to detect file type by recognition of binary signatures.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
TrIDNet - TRIDNet is the GUI version of TrID, probably more practical to use than the CLI version, especially...
Gramlee.com - Online grammar check, proofreading and copy editing services.