Get It Write
Get It Write: Who and Whom
Use the four-step trick that's on this grammar tips site and you will never have to wonder which to choose, "who" or "whom," again. There is a self test at the end of the article.
University of Calgary
University of Calgary: Practice Distinguishing Clauses
This section of an online grammar guide from the University of Calgary provides a review of and an interactive exercise on identifying how clauses function in sentences (as nouns, adjectives, or adverbs).