Okay here is what I know. Most of it isn't particularly surprising, and the 2 newcomers I know of don't interest me.

Veterans:

Captain Falcon
Ganondorf
Ness
Marth
Sheik (Zelda transformation of course)

Newcomers:

Wolf (this is entirely from that guy's GameFAQs post, see below, so I don't know if he's playable or an assist or what.)
Lucario (from 2 sources so I'm pretty sure he's in)

Stage:

Green Hill

Music:

Green Hill music is not confirmed, but there is quite a bit of Sonic music, specifically at least one from Sonic CD

Source 1:

A friend sent this: 

http://i2.photobucket.com/albums/y39/chupelo/gamefaqs.jpg

That was too spot on to be a guess.

Source 2:

An online acquaintance who knows somebody at Nintendo. She predicted the ability to have multiple BGMs per stage before it was on the blog, and also claimed Lucario was in. She's the one who talked about the Sonic music, Green Hill, and Marth. I trust her more than the GameFAQs guy, of course.

well I like the wi-fi. I'll be playing online till my hands aches and then i'll be using with my tounge

You do realize wolf is fox's alternate costume right? Have you not seen the E for all videos?

 Also why was that saved into photobucket? If it was from a website and he either emailed you or im'ed  you all he had to do was right click and copy image location. People at Gamefaqs should not be trusted plain and simple. 

 Ganondorf and Zelda are only semi-confirmed because resumes from the voice actors where found somewhere, I don't know exactly where though, and thus led to speculation. I expect Falcon to return, just not become simply announced since Sakurai has made no mention of secret characters and has only focused on the starting line up. The samurai goroh assist trophy kidna gave him away though, if the trophy's in their and falcons not then theirs something up.

We've seen screen shots with Ganondorf on the player select menu.

We did? In Brawl? o_O Don't recall.

Is online going to suck because of slow connections? I've got a 1.5M connection, but my stupid wireless router slows it down to 600K. Does anybody know how that kind of connection would work for an online game like SSBB? Maybe someone with experience on another online game?

stop making stupid posts sister.

and I want Wolf in. But Fox does have that costume. -_- I expect Falco to return. I wanted Fox/Falco/Wolf. With Falco de-cloned and Wolf with a new moveset. 

I really want this game and if they are using Zelda's TP form then why would they still have Sheik?

Characters who should be in brawl

Godzilla
Batman
Shaq
Aaron Carter
Abraham Lincoln
Optimus Prime
Jacki Chan
Indiana Jones
Care Bear
Chuck Norris
Gandalf the Grey/White
Black Knight
Benito Mussolini
Blue Meany
Cowboy Curtis
Jambi the Genie
Robocop
Terminator
Captain Kirk
Darth Vader
Lo Pan
Superman
Power Rangers (Red, Blue, Yellow, Pink, Black)
Bill Preston
Theodore Logan
Spock
The Rock
Dr. Octopus
Hulk Hogan
Mr. Rogers

 It's not impossible, I mean, just cause she DOESN'T turn into shiek doesn't mean she CAN'T