Not only can you watch the opening segment of Green Lantern: The Animated Series right now, but the one-hour sneak peek of the series has been announced for November 11, 2011 AKA 11.11.11.
The space based environments actually look pretty good so far, its when the actions gets planet side that the environments look a bit bare. I have to say though, this is a pretty strong scene. As for the Red Lanterns Zilius Zoxand and Razer, they seem like real punks, which I guess is the point, though they are a little light on the rage.
Check out a couple of previously released scenes here.