Antidote HD, the best and the latest in software designed specifically to help students with their writing assignments by including a very complete spell checker, an on-board French dictionary, a sophisticated thesaurus as well as grammar and syntax guidelines.
Orthonet, guide to French spelling, grammar and vocabulary.
FranceTerme, site dedicated to terms recommended by the Journal officiel.
WordChamp, the Language Learning Network, a web site designed for learners and teachers of foreign languages.
Le Bon Usage An excellent guide to the French grammar and how to avoid common mistakes.