There's also the classic of people leaving for San Jose Costa Rica and landing in San Jose California. Happened to a friend of mine, he wasn't too embarrassed by it because he shared the whole story on Facebook
Don’t know if it is still true, but Alaska used to have a daily flight from San Jose to San Jose. I always found that amusing when I saw the monitor waiting for my Portland (Oregon) flight.
I did the same mistake and only figured it out when checking in because there was a fee for checked luggage; there's no fee only for international flights, only for US/Canada flights.
I've almost done the reverse. I avoided actually booking the flight because I was trying to figure out why it was routing me from Illinois to Miami to get to California...
