http://www.muc.de/~hm/linux/linux-isdn.html
is a good place to start. There is a FAQ that suggests several cards.
AFAIR, you shouldn't use the AVM (Fritz) cards, because the developers
don't disclose the specs and so the timer couldn't be disabled, causing a
lot of interrupts.
I personally use Teles 16.3, cheap, working fine and I don't have to use
the toll intensive software update hotline like WinDOS users ;-)
(Did you know that noone is allowed to put the drivers on his
FTP/WWW-Server? They want their customers to use their 0190-hotline, where
they earn from the telephone tolls!)
Kurt
-------------------------------------------------------------
If you put a PC-formatted disk into a Macintosh, you can read it.
If you put a Mac-formatted disk into a Win95-PC, it asks you
whether it should format it.