austin bergström international airport
[airport code: aus]
20 minutes to downtown austin by car/taxi

dallas/fort worth international airport
[airport code: dfw]
3 (not so nice) hours to austin by car
on highway 35

he-who-must-not-be-named intercontinental airport in houston
[airport code: iah]
3 ½ (slightly nicer) hours to austin by car
on highway 290