There's a huge rich vein of great stuff out there that punches holes in the old category boundries. You're right to suspect that ECM is a good place to start, (Eberhard Weber "The Following Morning" or "Endless Days" are a couple of my favorites). You might try Louis Sclavis "Les Violences de Rameau" and Kenny Wheeler "Deer Wan"... there are dozens of other ECM releases that are equally good. The "Group Therapy" disc by the Jim McNeely Tentet (Omnitone) really seems fresh and alive, (you get a very nice interpretation of a Coltrane and a Bud Powell composition on this one). One recording that came to mind right away while reading your post was Beirach/Hubner/Mraz "Round About Monteverdi", the title (i know cor-ny) probably doesn't grab you, but the recording quality and the playing here will. Here are a few other possibilities:
Kamikaze Ground Crew/Senic Route
Franz Koglmann/L'Heure Bleue (this one is on Hat, Ejlif is right as usual)
Univers Zero/The Hard Quest (More ominous chamber music than what most people think of as jazz)
Tom Varner/Long Night Big Day
Wayne Horvitz/Sweeter Than The Day
Nils Wogram/Speed Life
Volapuk/Volapuk (Twisted Hungarian folk dance energy...maybe like if Bartok had an instrumental rock band w/ only cello drums and clarinet).
Giorgio Gaslini/Masks
Jerry Granelli/Another Place
Kamikaze Ground Crew/Senic Route
Franz Koglmann/L'Heure Bleue (this one is on Hat, Ejlif is right as usual)
Univers Zero/The Hard Quest (More ominous chamber music than what most people think of as jazz)
Tom Varner/Long Night Big Day
Wayne Horvitz/Sweeter Than The Day
Nils Wogram/Speed Life
Volapuk/Volapuk (Twisted Hungarian folk dance energy...maybe like if Bartok had an instrumental rock band w/ only cello drums and clarinet).
Giorgio Gaslini/Masks
Jerry Granelli/Another Place