There are several bus routes going to and leaving from Dublin Airport.

Aircoach

Prices: Adult Single €7.00, Return €12.00 (to the City Centre)

Route 1: Dublin Airport to City Centre, Ballsbridge, Leopardstown.

Route 1: Dublin Airport to Greystone and Bray.

Site: http://www.aircoach.ie

Airlink 747 and 748

These buses are operated by Dublin Bus.

Prices: Adult Single €6.00, Return €10.00

Route 747: Dublin Airport to the Central Bus Station (Busaras)

Route 748: Dublin Airport to Heuston Station (train station)

Site: http://www.dublinbus.ie/en/Your-Journey1/Timetables/Airport-Services

Irish City Link

Routes: Dublin Airport to Dublin City Centre and Dublin Airport to Galway.

Coaches are equipped with Wi-Fi.

Departures from the Coach Park, across the road from the Arrival Hall.

Site: http://www.citylink.ie/dublin_airport.php

Flybus

Single ticket: 9 euro (Adult)

Return ticket: 15 euro(Adult)

Route: Dublin Airport Coach Park, Foot Bridge N.4, Liffey Valley S/C, Clarion Hotel Liffey Valley, Bewleys Hotel Newlands Cross, Belgard Inn, The Square Tallaght.

Site: http://www.flybus.ie

Urbus

Prices: €1.50 to Swords, €5.00 to Castleknock, €4.50 to Blanchardstown

Routes: Dublin Airport to Swords, Castleknock and Blancharstown

Site: http://www.urbus.ie

All the info provided is subject to changes, please check the carriers websites for the most current details.