ELFE
Elementary French Exercises (or, ELFE) are French language drills to practice grammar and vocabulary. They are organized by subject, so you can easily focus in on your areas of difficulty.
The interface is sensitive so make sure to add accents and punctuation exactly as needed. Although it’s a bit old-school, the exercises are well-designed. They give corrections immediately. And it’s all free!
ELFE is accessible through Moodle.
Trésor
Trésor is a detailed online French language resource with several important applications. First, search your desired word, then toggle between tabs to see:
Morphologie – all morphologies of your word, including conjugations.
Lexicographie – traces your word to its root word and definitions, as well as common cultural usage and example sentences.
Etymologie – etymology and history of your word.
Synonymie – synonyms.
Antonymie – antonyms
Proxemie – installs an extension for your web browser.
Concordance – finds examples of your word in common books or texts
This is an extremely powerful resource, and if you install their toolbar or extension, you won’t need to navigate to the site each time.
Trésor is tout en français.