Some of the biggest and most popular free language learning websites include Duolingo and Memrise. Both sites are completely free and can teach someone French from scratch.
Duolingo shows pictures paired with French words and asks users to identify the equivalent of a given word in their native languages. It also asks users to translate sentences containing words from the lesson from French to their native language and vice versa.
On Memrise, users can choose from hundreds of courses, both official and user-made. Users are given translations of new words. Throughout the lesson, they are prompted to type the translation or choose the equivalent of learned words from a list. Users can choose "mems", small phrases playing on the meaning and pronunciation of the word, to help them remember words.
Both sites use spaced repetition to help users remember words and provide clips of the words or phrases pronounced by native speakers.