So I've never really told anyone that I am a HUGE fan of the show Smallville. If you're not familiar with it, it's the origins of Superman as a young man. The show started with Clark Kents freshman year in high school. It's now in Season 8 and is awesome. What they've done with the Superman characters is kick ass. They've modernized them and made em cool again. To see the the Justice League along with all the villains is really cool. Not to mention the way they show how Superman discovered his powers 1 by 1, it's season 8 and he still doesn't know he can fly. He doesn't even have the Superman costume yet...good stuff!
I'm currently watching season 7 and Supergirl just debuted...WHOA! To say she's UBER HOT would be an understatement.
Here are some of the other characters that have debuted...
Justice League - Impulse, Green Arrow, Clark Kent, Aquaman, Cyborg
That's just a few of the more frequently used characters. Martian Manhunter is a regular now, and Black Canary debuted this season. So far not many popular villains, other than Lex Luthor have been used, but a lot of "Villains of the Week" are used.