The title says it all: via CNN, we learn that a comprehensive study published today in Science (for those with access, the article can be read here) shows that girls perform just as well as boys in mathematics. This study is the largest and most detailed of its kind, comparing 7 million children from grades 2 to 11. The only weakness I can see at first glance is that the study used "No Child Left Behind" standardized test scores as its metric, and standardized testing is rather limited in its ability to capture true aptitude.
The results aren't surprising, though; in my personal teaching experience I've typically found that girls do better than boys in physics. This is a limited sample, and skewed by the depressingly small number of women taking physics classes, but I've never had any doubts of women's ability to succeed in mathematical and technical disciplines.
A good example of this is Emmy Noether (1882 - 1935), who in 1918 published what is now known as Noether's theorem, a general and far-reaching theorem which demonstrates the link between symmetries in physical systems and conservation laws. Conservation of momentum, for instance, is connected with the fact that the laws of physics do not depend on position. Noether's obituary was written in the New York Times by no less a distinguished mathematician than Einstein himself.