Airport puts flight information online: "In time for holiday travel, the Port of Seattle unveiled a new user-friendly Internet service Monday that will allow travelers -- and those providing rides to and from the airport -- to check real-time flight information."
(Via PI: Local News.)
I flew to SLC a few weeks ago, and they have a pretty good solution to the picking someone up at the airport case. They have a separate parking lot for people to wait in while waiting for people to arrive, and there's a big arrivals board there that tells people when the flight is scheduled to arrive, or flashes "PICK UP" (presumably a few minutes after it actually arrives).