Actuating a pneumatic solenoid manifold with Arduino
You could give a ULN2001 a shot: it's a pretty good jellybean driver. You can put the channels in parallel to drive higher currents (each is 0.5A).

http://datasheetcatalog.com/datasheets_pdf/U/L/N/2/ULN2001.shtml

The also have freewheeling diodes built-in so you don't have to worry about driving inductive loads like solenoid or stepper coils.