This site from Tex's French Grammar explains use of the subjunctive with expressions of doubt and uncertainty, interrogatives and negatives, relative clauses that express uncertainty and superlatives. Provides usage examples, dialogues...

This site from Tex's French Grammar provides a concise and clear presentation of bon/bien, meillure/mieux, aussi bon/aussi bien etc. Contains usage examples and interactive practice exercises (written and audio).

This site from Tex's French Grammar provides a succinct presentation of comparative adjectives (plus que, moins que, aussi que) and irregular adjectives (bon/meilleur, mauvais/pire). Provides usage examples, dialogues and interactive...

This site from Tex's French Grammar is a wonderful site with clear explanation of the "er" verbs, with usage examples and interactive practice exercises (written and audio).