Airports in Sardinia:

Cagliari Elmas. Cagliari can be easily reached by taxi or by shuttle bus operated by ARST (link in italian). The shuttle bus departs at the following times:
08:45, 09:30, 10:30, 11:30, 12:30, 13:30, 14:30, 15:30, 16:30, 17:30, 18:30, 19:30, 20:30, 21:00, 22:10, 22:30 and 23:00
The trip lasts about 10 minutes. Tickets can be bought in the airport at 0,67 Euro, or aboard of the shuttle at 1,19 Euro. The bus stop in Cagliari is in Piazza Matteotti, that is the main bus station.
Alghero Fertilia. Cagliari can be easily reached renting a car or by bus through Logudoro Tours (tel. +39 079 281728).
Olbia Costa Smeralda. Cagliari can be easily reached renting a car or by train http://www.trenitalia.com.

Additional information can be provided by Kassiopea Group.

Airlines:

Alitalia
Meridiana
AirOne
Air Dolomiti
Alpi Eagles
Ryan Air
British Airways
HLX.com

Travelling by Sea:

Tirrenia
Moby Lines
Sardinia Ferries
Grimaldi
Linea Golfi
SNCM.