This page holds the obligatory links collection. Not everything is directly related to audio, but most things should be useful to audio users and developers.
At present, there are two competing sound APIs for Linux:
In terms of technical merits, the ALSA approach is the way to go. While OSS has done a fine job of creating a lowest common denominator for audio interfaces among a number of UNIX platforms, it has many showstopper design limitations. (For example, decent support of professional multichannel hardware is almost impossible.) On the other hand, ALSA has a fairly good OSS emulation module which runs almost all (except some very hackish) OSS-compatible code. The ALSA drivers have been included since the 2.5 kernel tree to replace the OSS-based ones.
For PowerPC users, Iain Sandoe's LinuxPPC page is a good place to start.