The airport is 15km south of the centre. Arriving flights are met by a Finnair bus to Oulu (€4.40). From the bus or train station you can catch local bus 19 to the airport (€2.50, 25 minutes).
There is a good network of local buses. Each ride costs about €2.50, and route maps are displayed at bus stops.
The main roads north and south from Oulu are motorways (freeways) which are off-limits to cyclists - fortunately there are many minor roads and bikeways. Pick up a bike route map at the Oulu tourist office.