I really like a book called Word Power by Kaplan. It gives something like 50 lessons with a selection of words, sentences using them in context, pronounciation of the more difficult ones, and little quizzes/exercises at the end of each chapter to test yourself. It also divides the book into a couple of sections for the easier, tougher, and really obscure words.
But anyway, I found that to be very helpful! (especially since I feel my vocab is really pathetic!-at least compared to my family!)