There’s a worthwhile article on code reviews at developer.com at the moment called Effective Code Reviews Without the Pain.
Its a quick read, and the title says it all. The article’s focus isn’t so much on what your code review should cover, but how your code review should be carried out – how to make what can feel like a very adversarial, negative process into a postive, learning process. There’s tips for both the code reviewer and reviewee, with points like “Avoid ‘Why’ questions” and “Remember that the code isn’t you”.
Good, common-sense stuff. Its rare to find a development area that doesn’t use code reviews nowadays (even if only intermittently! 
), so it should be worth a read for most developers.