Introduction
There are a variety of sound libraries that can be used in Delphi and FreePascal/Lazarus. They all differ in terms of stability, reliability, features, cost, and support. The developer is recommended to check each one of them to decide which better fits the particular project.
Audiere
Audiere is an open-source audio library capable of playing MP3, Ogg Vorbis, FLAC, WAV, IT, XM, S3M, and MOD files.
AudiereSoundLib
A wrapper with VCL component for Audiere. Originally posted here.
BASS
BASS is an audio library running on Windows and MacOSX. It is available in a tiny DLL (about 100 Kb) and provides support for sound samples, streams (MP3, MP2, MP1, OGG, WAV, AIFF, custom generated, and more via add-ons), MOD music (XM, IT, S3M, MOD, MTM, UMX), MO3 music (MP3/OGG compressed MODs), and recording functions.
TBassDLLPlayer
BASS wrapper for Delphi 6 or higher. The files were taken from original post in German located here.
ZXLib
Visual Components for BASS sound library. This file was originally posted here.
SquallSound
SquallSound is a free sound system that is capable of MP3, WAV and OGG sound playback.
SquallSound.7z
SquallSound wrapper for Delphi with all features supported. The discussion of this component can be found in this thread.
Other Projects
AsphyreSound
This is a small audio wrapper for DirectSound with support for 2D/3D sound effects.