The Open University, LanguageTutorial.org, Surface Languages and the University of Texas all offer free online Latin courses. The first three sources use a traditional format in their course offerings, while the University of Texas teaches by examining original Latin texts.
The Open University offers a basic Latin course free to the public and further Latin courses for Open University students. Language Tutorial.org provides links to several different Latin tutorials including many lessons focusing on grammar.
Surface Languages teaches Latin using vocabulary and phrase-based learning. Its lessons include audio exercises, allowing students to improve both written and spoken skills.
University of Texas offers a 10-lesson course in which students learn Latin while reading parts of several works, including Livy's "History of Rome," Caesar's "Gallic War" and Augustine's "Confessions."