Not super exciting, but good, solid grammar practice

An online grammar textbook with clear explanations and examples

    Practice your grammar in this interactive series.
    Grammar topics
    Detailed grammar and writing lessons plus exercises.
    Lots of grammar and some vocabulary drills.
    Grammar and Mechanics
    Sign in to keep track of your progress online!
    Look under Stuff for Students and Stuff for Everyone.
    (Note: Click on the “Interactive Exercise” links to practice your grammar.)
    (Note2: You may also download handouts to keep track of your answers.)