Netflix's library of streaming content are a slew of animated titles from Marvel. While quite a bit of the series added are older cartoons that aren't available in HD, there's a few that are including Iron Man: Armored Adventures. Other selections that showed up this morning are The Incredible Hulk, Silver Surfer, Spider-Man Unlimited and more. There's a bit more information available at the Netflix blog, check that out and see what might be worth adding to your queue.
Update: Marvel.com has more details on what was added immediately, as well as other series (X-Men from '92-97) that will be arriving later this year.