Hi,
The Aztech PCI168 (AZF3328) has unmounted I2S output pins.
While some would consider this card to be an "el-cheapo heap of crap" (BTW, Windows hasn't bothered to support it in ages!), there's my pretty sophisticated Linux ALSA driver for this card which could be extended pretty easily to have support for the I2S port, too (simply copy&paste the existing DAC port code for the I2S port, that should work in a snap).
I intend to add code support for the I2S connector once there's better code modularization (the registers are simply 16 ports for DAC, 16 for ADC, and another 16 for I2S, which could be supported by one and the same functions each if properly abstracted, which sadly isn't the case yet).
Oh, and the Aztech ASC338 (Aureal Vortex AU8820 chip!!!) as well, it seems (unmounted connector "SPDIF_I2S", see e.g. the detailed photos at http://www.ssstjy.com/soundcard/aztech/AztechASC338A.htm )
However I have no idea how hard I2S support would be on that card's driver side OTOH...
Probably adding I2S was customary at Aztech, which were reputed for building high-quality cards at the time...
Heh, turns out LOTS of PCI cards sport an I2S output:
http://stason.org/TULARC/pc/sound-cards-multimedia/32snd_1.html
lists half a dozen or so (but, again, not sure about the driver side of things).
