Ugh, Apple's clear and white keyboards look great, but they are hard to keep clean. I take mine apart from time to time to clean it. I recommend having plenty of time so that you aren't rushed. I just carefully and gently pry the keys off (they just snap). I usually soak the keys in a bowl of water or clean thoroughly with alcohol. Also, with the keys off, you can get at the mess underneath the keys much easier. Again, I use alcohol.
Let the keys sit overnight to dry. You may want to flip them and let them sit another night to ensure they are dry before poping them back on the keyboard.
If your keyboard is really dirty, you can actually take it apart further. I don't recommend this unless you have lots of patience. The keyboard has screws that hold the plastic and white portions together. Just be careful that the little rubber "springs" don't go flying as you take it apart.
If you have patience, your dirty keyboard can be as good as new.
