Cassini has just made its closest approach to Enceladus according to its tweets. It closed to a distance of 50 kilometers, or 30 miles, from the surface of Enceladus. Cassini still needs to send the data it collected back to Earth, which it should start sending at about 9PM Pacific time today. However, they say some of the best images of Enceladus were taken after Cassini made its closest approach, where it took photographs looking back at the moon as it flew away. These images won't arrive at Earth until tomorrow.
NASA has an entire blog dedicated to this single flyby, so head over there to get the nitty gritty details.