There are lots of flight status sites out there. (My favorite is FlightAware because it’s the geekiest of them.) Many of them will send you email alerts when flight information changes, but the one from the Port of Seattle is the only one I know of that will also tell you when the arrival gate and baggage claim carousel number change, which is handy when you’re picking up someone at the airport. (Main entry page here.)
A useful site if you’re departing from the airport is the TSA’s Security Checkpoint Wait Times site, which gives you estimates of wait times based on data collected in the most recent few weeks.
When you arrive at Seattle-Tacoma International Airport, a friendly voice welcomes you via a pre-recorded message. Historically, the voice has been that of the mayor of the city of Seattle, but a few years ago, it changed to that of the President of the Port Commission. I don’t know what prompted the change, but I guess some sort of gentleman’s agreement fell apart.