Some ressources linked here comes from providers having a standalone version.

Le Littré is a well known french dictionary, download its freeware here.

Le Robert is another well known french dictionary, you can download it here (10 days trial).

I find Antidote to be a great electronic dictionary. It contains twelve dictionaries, eleven grammar guides, a powerful spellcheck and other useful information like synonyms, antonyms, conjugation tables and cooccurrences (words that work well together). It is a bit expensive though.

There is the Franqus, a web french dictionary made in Quebec (contains more informations about French American words).

i’m using this wiktionnaire.mobi ie the french wiktionary exported.