OSS is dead.
You should not be writing apps with
OSS.
Well, at least OSS has a programmer's guide (PDF
file):
http://www.opensound.com/pguide/oss.pdf
For ALSA
--------
Initial HOWTO's:
http://www.suse.de/~mana/alsa090_howto.html
http://equalarea.com/paul/alsa-audio.html
Reference manual for the PCM API:
http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html#pcm
Equivalents exist there for the MIDI API and others.
For JACK
--------
* the example clients directory contain sample code for
many different things. JACK is such a simple API
(no hardware configuration or format negotiation)
that these examples are enough to get many people
started without any further information.
* the reference manual is at:
http://jackit.sourceforge.net/docs/reference/index.html
Where is the equivalent for ALSA? Until it exists, we
will continue using OSS!
you're free to continue doing what you want but your software will not
interoperate with other audio software, it will not work without
card-specific hacks on various high-end audio interfaces, and at some
point in the not very distant future, it will rely on ALSA's OSS
emulation to run.
--p