Taking a good self-portrait is both a handy skill and a way to expand your photographic repertoire. Nathan Marx at Digital Photography School has put together a great tutorial on getting started with self portraiture. The tutorial covers basic tools you'll need and ways to make life easier when photographing yourself without an assistant to man the camera, like using a remote and tethering your camera for better feedback:
Most digital cameras have a mini video if not a HD video out. I borrowed my son's DVD player (the one he watches movies in the car with) on multiple occasions for the sole purpose of shooting self portraits. This is where the remote comes in great; you can fine tune the composition by watching that little monitor, without having to run back and forth. If you have a newer DSLR with an HD out then you could hook up your laptop or HD monitor.
I've frequently used tethering for macro work to make easier work of focusing ultra close-ups, but never considered how much easier it would have made taking self-portraits! In addition to mechanical tips, Marx also covers ways to incorporate lighting and thematic elements into your portraits for better variety and impact. For more tips on snapping yourself, check out how to take incredible self-portraits and remember that the principles of avoiding mediocre portraits apply to self portraits too.