In July, I'm taking a 7:30 a.m. flight from NCE to CDG from Hotel Le Grimaldi in downtown Nice, which means that I will probably need to be at the airport by 5:30 a.m. - any suggestions for transportation?
Either bus or cab. This website gives you details of the bus. http://wikitravel.org/en/Nice#By_plane. Cab is quoted between 20 - 30 Euro depending on the time of day. Even in summer I think things should be quiet at that time of the day so the cab could be cheaper than this price. As you have a flight within France you probably don't need to be there so early. You will need to allow for security checks especially with the liquid thing at the moment but 2 hours is more than enough.
According to the Nice airport site, buses don't start running early enough for you. It looks like you'll have to take a taxi.