I have a few that I love.
ECM - jazz label that has been around since the late 60’s. There seems to be a characteristic ethos running through most of their releasses. The vast majority of their releases are not typical jazz. Much of it is by European musicians, and has quite a bit of European music influences. Some may be classified as "chamber-jazz".
Their recordings are universally very good quality, with a lot of space, and percussion is typically recorded very well. They also made the transition to digital very well.
Kairos Music - Avant-garde and contemporary classical music label.
Lots of great, avant-garde classical. Musically, your mileage may vary, since most of their catalog is atonal, and "thorny" sounding.
Overall, very well recorded, with large, well defined soundstages, and great imaging.
Cuneiform Records - Specializes in avant-garde prog-rock, jazz, jazz-rock, and hard to categorize music.
Loads of creative, progressive, boundary pushing musicians and bands, with off the charts levels of musicianship.
Tend to be better recorded than most labels, but it is not always a given.
Brain Records - Now defunct 70’s and early 80’s German record label.
Specialized in Krautrock, prog-rock, and some jazz-rock.
Loads of progressive and experimental artists. Vere well recorded, pressed on the highest quality vinyl available. Much of their recordings were recorded by engineer, Konrad "Conny" Plank, who had one of the best recording studios in Europe.
A few modern progressive labels:
Inside Out, Laser’s Edge, K Scope

