There's no train connection with Cairo Airport as yet, but a subway line is being constructed that will connect the airport with Mohandesin station (in Giza) in 2012.
Car and bus
Cairo International Airport is situated 22 kilometers northeast of the Egyptian capital. Until recently the infrastructure was completely inadequate, but since the opening of a new toll road the situation has improved significantly. The airport is easily accessible by rental car from Cairo's ring road. The way to the airport is clearly signposted.
Several bus services connect the airport with the Egyptian capital. For tourists the shuttle bus is easiest. This bus runs to Heliopolis, Nasr City, Cairo Center, Giza, Mohandesin, Zamalek, Maadi and the pyramids. In the Arrivals Halls of both Terminals 1 and 3 you can buy a bus ticket (Tel. +20(0)2 2265 3938).
Car rental Cairo Airport
You can rent a car in the Arrivals Halls of both Terminals 1 and 3. Six car rental companies are present at Cairo Airport: Avis, Budget, Europcar, J Car, Hertz and Thrifty. You can also book a rental car in advance using the service provided by EasyTerra; they compare the rates of several providers in a single quote.
There are many taxis outside the Arrivals Hall, but you will already be approached by drivers promising you a 'good price' inside the terminal. Although sometimes this is indeed the case, you better first inform yourself about the going rates. You can for example ask a fellow Egyptian traveler. You can also book a taxi in advance online via Cairo Taxi. The ride to Cairo's center takes 30-60 minutes, depending on traffic.
There are large parking lots outside Terminals 1 and 3. You pay 5 Egyptian pounds per hour. There's a parking garage near Terminal 2.