Actually, he didn't stop time; he used the Mangekyo Sharingan to inniciate an extremely powerful genjutsu, which basically happens in the blink of an eye. He isn't manipulating time, but rather, making it seem so through an illusion. ... The name of the jutsu escapes me though, I havn't watched/read Naruto in ages.
Look at me... debating over Naruto. What has the world come to?! DX