More info at Capital Metro.
Interactive Map:
Google Transit Trip Planner - Austin.
Type in something like:
AUS to 6th & Brazos, Austin, TX at 7pm
or
AUS to 604 brazos, austin, tx
Wow.
This is going to be fast and inexpensive.
Airport Flyer Schedule [ .pdf ]
via [ SXSW Baby! Google Transit for SXSW ]