Over the weekend I got a Canon 430EX II Speedlight Flash to use during both night and daytime photography. Needless to say I am pumped. It giving me a whole new venue to experiment with and I recommend a hot shoe flash to any one interested in photography. I wager that a $300 flash will help your photography more than a $1000 super fast lens.
In addition to using my flash at night, I also use it in the daytime to illuminate faces and details. Here is an example.
Without a Flash.