As an interim summary, here are the stereo microphones that have been mentioned in this thread or that I've either remembered or found listed in various places since this thread began. Some models are not necessarily professional.
Additions or corrections? We love 'em.
Current:
AudioTechnica ATR25, AT835ST, AT815ST, PRO 24, BP4027, BP4029, AT822, AT825, AT849
Avantone CK 40
Beyer MCE 72, MCE 82
Cascade X-15[L]
Josephson C700S
Manley Gold Reference Stereo Microphone
Neumann USM 69, RSM 191, KU 100
Nevaton MC48
Pearl DS 60, TL 4[4], MS 2, MS 8, MSH 10, MSH 20
Peluso P Stereo (forthcoming)
Røde NT4
Royer SF-12, SF-24
Sanken CUW-180, CSS-5, CMS-10[MS], CMS-7s, CMS-9, CMS-2
Schoeps CMXY 4V, MSTC 64, KFM 6, PolarFlex system, Double M/S system
Sennheiser MK 418 S
Shure VP88
Sony (?)
Soundfield ST350, SPS422B
Studio Projects LSD2
THE BS-3D
Thuresson (?)
Violet Stereo Flamingo
Discontinued:
AKG C 24, C 33, C 34, C 422, C 426, C 522 ENG
Beyer MC 833 (?)
Gefell ZUM 64
Neumann SM 2, SM 23, SM 69, SM 69fet, RSM 190, KU 80
Schoeps CMTS 301, CMTS 501
Soundfield ST250
--best regards