In the beginning when Nano ran into that guy, in the manga she was running to school, not chasing her breakfast. In fact, the anime seems to imply she isn't going to school yet, in the manga she was already friends with other girls from the beginning.
Also, there was a scene involving Sasahara before the school assembly scene, so finding out he's not really rich is bit more of a surprise.
Other than that, it was mostly just adding small scenes not in the manga (or were a lot later than I read), like the one with Mai and her dog, and the fire alarm one (which I think was my favorite part of the episode).
edited 3rd Apr '11 1:53:30 PM by KuroBaraHime