The back of your textbook might help. If your teacher uses Wiley, that might be another resource. Other than that, try searching on Google and look up as you go.
And if you're of the synthetic kind of chemist, here are really tough ones (nowhere near the level we would test on an introductory organic chemistry course): SEARCH BY KEYWORD - CCB Challenging Problems
And if you're of the synthetic kind of chemist, here are really tough ones (nowhere near the level we would test on an introductory organic chemistry course): SEARCH BY KEYWORD - CCB Challenging Problems