TUAW reader Harris Rydal sent in a bunch of terrific suggestions for using Siri's built-in search features without having to do a lot of typing. These are exceptionally useful ways of taking advantage of Siri-to-Safari tasking.
Sports scores - Look up the current score for in-progress games and find the team record, last game score, and the upcoming game. Say "Yahoo team name score". Rydal points out "There is a 'Yahoo' here because mobile Yahoo formats the results better than Google."
Flight Times - Say "Search the web for flights from City/Airport to City/Airport". In Google, this brings up a list of flight times that day and the associated airline.