[Anime Online]

I'm not sure if this was pointed out earlier.

Spoiler for Novel#1 & #3: Why Haruhi cut her hair in Episode 02:

We know in Novel#1 (Episode 02), Kyon asked Haruhi about her daily changing hairstyle. After explaining, she asked if she had seen him before, a long time ago.

The very next day, she cut her long hair. It is alluded by both the anime and novel that it was because he asked her about her hairstyle.

Fast forward to Bamboo Leaf Rhapsody in Novel#3, we know Kyon went back in time and met middle-school Haruhi. From the novel, we know the length of her hair was past shoulder-length.

It would seem high-school Haruhi cut her hair to see if Kyon was the same person she met 3 years before and if he recognized her. In fact, she wears the same hairband as middle-school Haruhi did the night she met Kyon.