I just learnt that the German label Danza y Movimiento (DyM) are issuing a new series called Tango Classics. It is based on the collection of the collector Klaus Johns. There seems to be quite a few tracks not available elsewhere, for instance by Julio De Caro, so it should be worth checking out for all you serious collectors out there :-) Also listed at tango.info.
Unfortunately, they only offer mp3 downloads at the time, flac or some other lossless option would be very nice. And a less tacky cover wouldn’t hurt either… (That last one is a bit surprising given their previous issues)
EDIT (2011-05-03) DyM now offer flac downloads for members.