I ( A β Pseudolonewolf) compose music as a hobby, and for my games (though not all music I make is for games!), in the midi format, and most of it - years of work - is here to listen to for free.
There are advantages and disadvantages to the midi file format. It's great because the filesize is tiny; just a few kilobytes per file, meaning no long downloads. However, they may not play correctly for you, as their sound is determined by your own computer's midi player (since a midi is nothing but numerical data, telling different instrument sounds to play for different durations and at different pitches; the player provides the instrument sounds). They also cannot be put on mp3 players or anything like that in their raw format.
To hear the true sound of some of my game music, you can buy the Official Soundtracks using the links below. There are several sections of music. Click on one to see all the music in that section.