Looks like it came out pretty good, though the face looks (to me) as if unsharp masking with a fairly large pixel radius was used. Flash was only conspicuous in the eyes and the faint shadow behind.
When possible, it helps to shoot with most lenses, especially kit types, at f/5.6, or, even better, f/8, for maximum sharpness on the rebel xt. In a situation like the one here, I'd suggest setting the f-stop, then adjusting your ISO to get adequate brightness at a shutter speed at least equivalent to your focal length, I.E. 1/50th for 50mm, 1/200th for 200mm, etc. If it were me, I'd probably go with 1/80th or better there, just to be safe. If you're using flash, then the ISO may not need adjusting.
According to what I've read on these forums, that's a generally accepted ratio for reducing or eliminating camera shake blur.