I recently bought a powder sunscreen called go! screen. I liked the fact that it is a simple formula. I have been using it over Blue Lizard Faces spf 30, instead of my usual translucent powder, then applying my powder makeup. Even with reapplication later in the day over the powder makeup it doesn't look cakey.
There just doesn't seem to be a good way to deal with the whole reapplication part of sunscreen when you wear makeup. According to dermatologists you need to clean off the makeup and reapply the sunscreen. Not exactly practical. On days when I am outdoors all day I forgo a lot of makeup and can easily reapply, but on days when I am just out for a while later in the day? Just hope the powder sunscreen does work well enough to protect for those short stints outside or in the car.