The vast King Fahd International Airport (IATA: DMM) is about 50 km from the city centre, literally in the middle of the desert — you'll see sand dunes, camels and Bedouin tents on the way there. The world's largest airport by area, the airport is enormous and underutilized. Long-distance links are limited, but bmi flies from London and Lufthansa has flights to Frankfurt. All domestic and international flights leave from the same terminal. If you have time to spare and need a meal, head up to the fourth floor (above checkin), where you'll find an observation deck and a cafeteria serving up a simple buffet. Once through security, there are virtually no facilities aside from a snack stall and a book shop.
SAPTCO runs comfortable shuttle buses between the airport and the bus station roughly hourly (SR12). The trip takes around 45 minutes. Alternatively, taxis can cover the same distance in half an hour and charge upwards of SR50.
The SAPTCO bus station is on 11th St, some 700m north of the city center. There are regular services throughout the country, as well as SABTCO  buses direct to Bahrain five times a day; see the Bahrain article for details.
Dammam is well linked by the kingdom's modern highway network and the GCC road. Riyadh is 4 hours. Nearby Khobar is a 15 min drive, from where Bahrain is another half an hour by the King Fahd Causeway. Saptco runs regular buses.
Public transport is poor. Taxis and "dubbabs" dominate the market , and are usually used by the lower scale foreign workers. SR.2 is the standard fare for anywhere to anywhere! Best deal is thus the rent a car. Taxis charge 10-20 SR for trips within the city proper.