I can't believe I didn't see this among the Wii topics...
Confirmed Characters:
Mario
Link
Pikachu
Kirby
Fox (2nd trailer)
Metaknight
Pit
Zero Suit Samus (ZSS)
Wario
Snake (from Metal Gear Solid)
Yes, Nintendo includes third parties...
Stages:
Some stage called
HalberdA Pit stage
Fire Emblem castle stage
Metal Gear factory stage
Mario Kart stage
Yoshi's Island stage
Items:
Smash Token
Nintendog (?)
The Smash Token is supposed to give you some uber special move. The Nintendog is supposed to cover the majority of the screen, making it harder to fight (not as annoying as Togepi in Melee though).
What else am I forgetting... oh, right!
There is a
rumor that Baby Bowser, Ridley, and Dark Samus (I think) will be in Brawl. Also part of this rumor: Ice Climbers, Mr. Game & Watch will get the boot while Young Link will become Cel Shaded Link (the Link from Wind Waker).
Some characters (Pikachu, Wario, Snake) have the ability to crawl. Wario can crawl backwards.
Due to the confirmed stages, people speculate that Yoshi, Marth, Roy or another Fire Emblem character will be confirmed later on.
Sakurai has polls undergoing and on Smashboards I think it said somewhere that
the polls won't end until 6/9 and maybe this will make Brawl a holiday title for 2007.
I think Sakurai also said that
you can use Gamecube controllers to play as well as the fact that
clones (characters that have the same moveset as another character, like Falco to Fox or Pichu to Pikachu)
will be reworked or made more unique. If they can't do this with some characters, and if one of these characters is Dr. Mario, the simplest thing is to make Dr. Mario a costume for Mario.
Geez, that's a lot of typing! Anyone is free to remind me about any mistakes I made as well as suggest or mention something I may have forgot. Most facts were courtesy (I hope I spelled that right) of IGN (thank you).