DungeonPack Mod 1.7.2
Adds many new structures to the game, most of which are hostile and contain loot! Also good for a free home once you clear out all the baddies.
Temple Of Death
You can disable/enable dungeons, set the spawn rates, change the sizes etc…. Just create a new world an try little bit around. To make a dungeon spawn more often you have to lower the rarity.
DungeonPack also supports mod biomes from mods like Biomes o Plenty or ExtraBiomesXL.
Download DungeonPack Mod 1.7.2/1.6.4/1.6.2/1.5.2