UPDATE November 2010. The RCA airport shuttle (line n° 210) timetable has changed slightly. The last one leaves Cannes from close to the Mairie/town hall at 7pm! That’s right, after 19h, you will have to fork out €70-90 to get to the airport from Cannes. The bus n° 200 that goes through Antibes does run until 8.10pm (8.30 on Sundays and holidays), but it takes between an hour and 90 minutes to get to the airport and stops at Terminal 1. For the latest timetables, check the RCA timetable (in French).
If you intend to leave Cannes after 7pm, I strongly recommend planning ahead and sharing a cab or taking the train.
People going to Cannes from the airport can catch the last express shuttle at 8pm. The next buses, at 8.45 and 9.55, take the coast road with a journey time of between one hour and 70 minutes.
Prices are €15.60 one-way, €25.50 return. Reductions for people under the age of 26 (€12.50) and groups of four people (€41).