I wouldn't normally post anything like this off of IMDb, but the fact that this guy was apparently the first person to reveal the after-credits scene for THOR, does give him a little more credibility than your average forum user. There's some really interesting stuff below and while I'm a little dubious about some of it, it sounds pretty good for the most part. What's even more interesting is what the guy doesn't mention, but I'll keep an eye on things and will be sure to post more spoilers if and when they become available.
WARNING: MAJOR SPOILERS AHEAD!!!
*It starts like The Ultimates with Captain America in WWII*
*There is a battle between Captain America and some S.H.I.E.L.D agents*
*The Skrulls are in it but they are not named. They aren't Nazis like in The Ultimate and there is no Kree unfortunately. Loki DOESN'T summon them, he's simply tells them the cube's on Earth*
*Final battle is: Loki vs. Thor in the air, Hulk and Captain America and Hawkeye and Natasha against some Skrulls on the Helicarrier and Iron Man and Nick Fury on a spaceship vs. the female leader of the Skrulls Anelle (turned out to be posing as Maria Hill)*
*Coulson is killed by Anelle*
*It ends with the Avengers realize they don't work out as a team so they're split up (until next time?)*
*There is no real leader to the team, though it feels more like it's an Iron Man-Nick Fury-Thor based the most*
UPDATE: The guy claiming to have read the script has now answered a few questions about it, but may have tripped himself up. If Loki is using the Cosmic Cube to summon the Skrulls, why would Fury start assembling a team to combat them way before the events of Thor even took place? Here's what he said anyway:
Is there a Avengers VS the Hulk battle?
-Yes, a short one.
How does Loki meet the Skrull and why do they want the cube?
-They want to resurrect their dead planet with it's power.
Why is Fury assembling The Avengers in the first place
-To fight the Skrulls.
To a certain degree, all of the above information is somewhat believable. However, I'm just not buying it. I'm also pretty sure that if this all were the real deal, Marvel would have already asked for it to be taken down. Still, there's no harm in speculating, so be sure to share your thoughts below!
With an all star cast which includes Chris Evans as Captain America, Robert Downey Jr as Iron Man, Chris Hemsworth as Thor, Mark Rufallo as Bruce Banner, Jeremy Renner as Hawkeye, Scarlett Johansson as Black Widow, Cobie Smulders as Maria Hill, Clark Gregg as Agent Coulson, Samuel L. Jackson as Nick Fury and Tom Hiddleston as Loki,
The Avengers is set to be released on May 4, 2012!