Since there was no universal (and up to date) repository of OpenAL extensions, I've decided to compile information available from different sources. As for now, a lot of these descriptions are only stubs or extracts from headers.
If you have more detailed description of a specific OpenAL extension (or would like to provide list of extensions available on a specific platform), please issue a pull request.
All information is also available with Github wiki: https://github.com/openalext/openalext/wiki
AL_EXT_ALAW AL_EXT_BFORMAT AL_EXT_DOUBLE AL_EXT_EXPONENT_DISTANCE AL_EXT_FLOAT32 AL_EXT_IMA4 AL_EXT_LINEAR_DISTANCE AL_EXT_MCFORMATS AL_EXT_MULAW AL_EXT_MULAW_BFORMAT AL_EXT_MULAW_MCFORMATS AL_EXT_OFFSET AL_EXT_source_distance_model AL_LOKI_quadriphonic AL_SOFT_block_alignment AL_SOFT_buffer_samples AL_SOFT_buffer_sub_data AL_SOFT_deferred_updates AL_SOFT_direct_channels AL_SOFT_loop_points AL_SOFT_MSADPCM AL_SOFT_source_latency AL_SOFT_source_length ALC_ENUMERATE_ALL_EXT ALC_ENUMERATION_EXT ALC_EXT_CAPTURE ALC_EXT_DEDICATED ALC_EXT_disconnect ALC_EXT_EFX ALC_EXT_thread_local_context ALC_SOFT_HRTF ALC_SOFT_loopback ALC_SOFT_pause_device ALC_SOFTX_device_clock
AL_EXT_EXPONENT_DISTANCE AL_EXT_float32 AL_EXT_LINEAR_DISTANCE AL_EXT_OFFSET AL_EXT_SOURCE_NOTIFICATIONS AL_EXT_STATIC_BUFFER ALC_ENUMERATION_EXT ALC_EXT_ASA ALC_EXT_ASA_DISTORTION ALC_EXT_ASA_ROGER_BEEP ALC_EXT_CAPTURE ALC_EXT_MAC_OSX
AL_EXT_EXPONENT_DISTANCE AL_EXT_float32 AL_EXT_LINEAR_DISTANCE AL_EXT_OFFSET AL_EXT_SOURCE_NOTIFICATIONS AL_EXT_SOURCE_SPATIALIZATION AL_EXT_STATIC_BUFFER ALC_ENUMERATION_EXT ALC_EXT_ASA ALC_EXT_ASA_DISTORTION ALC_EXT_ASA_ROGER_BEEP ALC_EXT_CAPTURE ALC_EXT_MAC_OSX
AL_EXT_EXPONENT_DISTANCE AL_EXT_LINEAR_DISTANCE AL_EXT_OFFSET AL_EXT_SOURCE_NOTIFICATIONS AL_EXT_SOURCE_SPATIALIZATION AL_EXT_STATIC_BUFFER ALC_ENUMERATION_EXT ALC_EXT_ASA ALC_EXT_CAPTURE ALC_EXT_MAC_OSX ALC_EXT_OUTPUT_CAPTURER