Shooting good-looking images with flash is surprisingly hard. A friend of mine who went down that route and spent the better part of a year learning shooting with flash recommended this book:
http://www.amazon.com/Light-Science-Magic-Fourth-Introductio...
Also, you should learn how to use Lightroom, Aperture, Bibble or similar for post processing. (If you understand how the postprocessing tools work you can shoot with that in mind).
But most important: shoot every day. Practice as often as you can. Bring your camera with you everywhere. If you shoot a few thousand frames per month for a year you are bound to learn something.
Peter Norvig has a good summary of the basics on his web page: http://norvig.com/dance-photography.html
http://www.flickr.com/photos/fledsbo/
In 2010 he set himself a goal of shooting one picture every day:
http://www.flickr.com/photos/fledsbo/sets/72157622990857973/
That's a good example of how to become a good photographer in just a year. (If you click through his photo stream you'll find a lot of interesting images that were shot with flash).
I strongly suggest checking it out if you're a serious photographer. Http://strobist.blogspot.com
Assuming built-in flash alligned with the camera lens. You can mitigate a lot of this with bounce and slave units. Still, I'm finding that natural lighting and a small tripod (even a 6" mini braceable on a wall or pole) does wonders and makes for some stunning photos. At other times, even motion blur can be useful (especially for night/club shots).