Of course, several of these *coughBatmancough* have many, many versions. I'll just go by character, though. You know what you have. I'll also be listing some more than once, because they belong to several groups.
Superman Family:
Superman (duh)
Lex Luthor
Brainiac
Cyborg Superman
Steel
Bizarro
Supergirl
Darkseid
Power Girl
Batman Family:
Batman (WHO KNEW?!)
Riddler
Batgirl (Cassandra Cain)
Batgirl (Barbara Gordon)
Catwoman
Joker
Man-Bat
Nightwing
Robin
Bane
Batwoman
Clayface
Harley Quinn
Killer Croc
OMAC
Penguin
Green Lantern Corps:
Hal Jordan
John Stewart
Guy Gardner
Salaak
Kilowog
Sinestro
Star Sapphire
Justice League:
It would be easier to list which characters do NOT fit into this category.
Ma Hunkel Red Tornado
Batwoman
Blackhawk
Golden Age Flash
Mary Marvel
Nightwing
Raven
Robin
Stargirl
S.T.R.I.P.E.
Salaak
Sgt. Rock
Starfire
The Question
Wildcat
...all others have been in the Justice League, or have fought the Justice League, at some point. And actually, I could be wrong about a couple of the ones I listed.
Justice Society:
Batman
Superman
Wonder Woman
Dr. Fate
Golden Age Flash
Hawkgirl
Hawkman
Ma Hunkel Red Tornado
Captain Marvel
Power Girl
Stargirl
S.T.R.I.P.E.
Spectre
Wildcat
(Teen?) Titans:
Robin
Nightwing
Starfire
Cyborg
Flash (Wally West)
Raven
Supergirl
Deathstroke
52 (I like this idea^^):
Steel
Booster Gold
The Question
Batwoman
Starfire
Lobo
Ambush Bug
(Now I wish there had been an Animal Man and an Adam Strange madeT_T)
And, for fun, Characters Who Have Died and Come Back to Life:
Superman
Blue Beetle
Flash (Barry Allen)
Raven
Aquaman
Green Arrow
Hal Jordan
Sinestro
Hawkman*
Lobo*
Wildcat*
And Batman, if you count being currently dead, but guaranteed to come back within the next year or so
(*Not sure if they count, since dying and coming back is part of their power...meh, whatev)
It may, in fact, be the most beloved of story arcs DC has put out in quite a long time. If only they hadn't tainted its memory with Countdown...
Not so far as I've ever seen or heard. They were part of the famous Giffen/DeMatteis-era Justice League, though.
After Hal Jordan died, he became the Spectre for a goodly number of years. That's not the version which was made into a minimate, though.
Hal's been alive since about '04. The Spectre was hostless for a while, but became Crispus Allen during Infinite Crisis. And yeah, the minimate is based on the Jim Corrigan Spectre. Obscure knowledge of DC characters ftw.