Young Justice producers Brandon Vietti (Batman: Under the Red Hood) and Greg Weisman (Gargoyles) revealed the following to 109 at NYCC..
Greg Weisman: We're adapting Teen Titans, we're adapting Young Justice, we're adapting the whole DC Universe. We're set on Earth 16 in the DC multiverse and we're sort of making ours a young universe. Superman's only been around 10 years, the Justice League's only been around three or four years. Robin's been around four years. The others have been doing it for even less time. Speedy for three, Kid Flash for two, Miss Martian hasn't done it at all yet when our series starts. So we're keeping it young.
Brandon Vietti: It's a show about teenagers who happen to be superheroes [...] They're a cover ops unit, and that will have repercussions in their lives, with their mentors, their parents, all kinds of things [...] The villains we will see are Mr. Freeze, Icicle Junior, Killer Frost, Captain Cold, and Black Manta are the five that we're revealing, obviously there's a lot more.
GW: Last time I checked, we had over 150 DC heroes and villains in the show. We have a really small handful of original characters in the show. From the Justice League, the big three are Batman, who assigns them they're missions; Red Tornado, who is their den mother; and Black Canary is in charge of their training. The other characters include their individual mentors (like Superman and Martian Manhunter), other heroes like Guardian and Speedy, and the Justice League, whose line-up includes Wonder Woman, Captain Atom, Captain Marvel, Zatara, Hawkwoman, and others. We have a 16 member Justice League. [...]
Well, they really like their icy villains don't they? A preview of Young Justice will run November 2011 on Cartoon Network and the series will officially debut Spring 2011. Io9 also have some news on the upcoming Green Lantern Animated Series, but I'm not sure it's anything we haven't covered before. Click the link below to check it out for yourself.
Here is a video interview, and first look at the show.