University of Texas at Austin
Tex's French Grammar: Contractions of a and De
This lesson from Tex's French Grammar is a wonderful site with clear explanation of forming conntractions with the prepositions "a" and "de", with written and audio usage examples and interactive practice exercises.
University of Texas at Austin
Tex's French Grammar: Prepositions With Places
Tex's French Grammar clarifies the usage of prepositions (a, de, d', du, des, au, en, aux) with regard to geographic locations--and gives usage examples and interactive practice exercises (written and audio).
University of Texas at Austin
Tex's French Grammar: Partitive Articles
This site from Tex's French Grammar is a wonderful site with clear explanation of the partitive articles, with usage examples (written and audio) and interactive practice exercises (written and audio).