LanguageTool is a web-based grammar tool, useful for correcting texts in many languages or for checking your spelling. 
LanguageTool supports a large number of languages, including many not offered at Reed. These include: Asturian, Belarusian, Breton, Catalan, Dutch, Esperanto, French, Galician, German, Greek, Italian, Japanese, Khmer, Perrsian, Polish, Portuguese, Romanian, Russian, Chinese (Simplified), Slovak, Slovenian, Spanish, Swedish, Tagalog, Tamil, Ukranian.
LanguageTool is much more powerful than its competitors BonPatron and Reverso, allowing 20,000 characters (about 2,500 words). It also allows for correction of different dialects/regions, e.g., Swiss and Austrian German, or Brazilian vs Portugal Portuguese.
Grammatical explanations are only in the language, for example French or German. LanguageTool also has a useful Google Chrome extension and a Google Docs add-on, which allow the user to correct text while typing online or in a Doc, as well as an add-on for Microsoft Word.