Sounds: WAV, AIFF, MP3, MP2, MP1, OGG
Load, play, pan, set volume, loop, fadein, fadeout, crossfade. Each sound effect can have any number of instances which means, say you load a shot sound. Give it 3 instances, and every time you play the shot sound it will automatically cycle through the 3 instances. This stops the stutter effect from using the same sound over and over.
MP3 files are treated as sound effects by the way.
Music: MO3, IT, XM, S3M, MTM, MOD, UMX
Load, play, loop, set volume, fadein, fadeout, crossfade. Very easy to use. These formats take up more system resources than sound effects, so you'll have to decide for yourself how it affects your game. For a fast action shooter I might go with looping mp3 or ogg sound fx than using music formats. Hard to tell at this point? I've only had a trickle of users report mods not working on their machine in the past. Seems to be a very low percentage not being able to play these formats.
It's free for all uses. Download, have a look. If you have any questions or problems, post them in the forum.