Barcelona Airport Transport: Bus line 46

The TBN bus line goes from Plaça Espanya to Terminal 1, stopping also at the Terminal 2. The line travels between 5.00 am and 24.15 am.
The 46 bus line is slower than the Airbus Shuttle and it is not recommended if you are running out of time soon. It is however a cheper way to get to the airport and get a last view of the city before departure.
Detailed information about the route and the schedule can be found here:
http://www.tmb.cat/en/linia-de-bus/-/bus/46/detall-s/sentit-Aeroport/dia-FEINER/parada-1064

Price:
single trip: 2.00 EUR

Can be used for free with the Barcelona Card 

For night transfers to and from the Barcelona Airport, view the information about the NitBus N17 bus line:
http://barcelona-holiday.blogspot.com/2012/04/barcelona-airport-transport-nitbus-n17.html