SuperJedi224's Nether Dungeons

Here's a little mod that generates nether brick structures similar to overworld dungeons at various locations throughout the nether. With default settings, it will attempt to generate approximately one dungeon per four nether chunks (though not all generation attempts will be successful). Each dungeon contains a monster spawner (can be either blaze, skeleton, wither skeleton, or spider) and either one or two chests.

The source code can be found here.