XXY is usually male, with some females. I did a big case study on a guy that had a sex change because he was XYY. He was a really girly male to begin with and said he never felt right until he became a she through surgery.
Oh, XY is not always male either. Just the majority of the time. There are people with andro resistance and they end up being female but sterile. You couldn't tell by looking at them and there is just as much testostorone running through them as any man, but it has zero effect and they behave, look, and are girl through and through except the being sterile part and having a ton of extra testostorone.
XO is usually a still born nothing. It remains a fetus that is sexless. Or if born, a female with very few female characteristics... the "Pat" if you will.
Turner syndrome (XO syndrome, monosomy X, missing Y): This should just be called the "X syndrome" because the person has an X, but no second sex chromosome. Such people are female, as there is no male Y chromosome. It is a 1-in-5000 syndrome, involving some relatively minor conditions, but usually sterility.
Klinefelter syndrome (XXY syndrome, also rarely XXXY): a 1-in-1000 disorder where the person is usually male (because of the Y chromosome), but has lower levels of testosterone and may have some female-like features (because there are two X chromosomes), and is usually sterile. The rarer XXXY syndrome may lead to retardation.
Jacobs syndrome (XYY syndrome): The person has an extra Y male chromosome. He will be male and may be largely normal, or may suffer from minor features such as excess acne and may be very tall, and in some cases behavioral complaints such as aggression. Frequency around 1-in-2000.
Triple-X (XXX, also XXXX or XXXXX): These people are females with an additional X chromosome. In rarer cases, there can even be 4 or 5 X chromasomes. They can be largely normal, or may suffer from problems such as infertility (some but not all), and reduced mental acuity. Occurs with a frequency around 1-in-700.