X-ray Mod might be a popular choice, but Xray Ultimate Resource Pack is much easier to use. So that you can see through things more easily, also turn off smooth lighting.
Be sure to pick up Optifine if you want the extra night vision effect.
Do you need help finding ores and minerals in Minecraft? If so, then Xray Ultimate Resource Pack is the perfect solution for you! This pack shamelessly highlights all of the ores and mineral blocks in the game, making it much easier to find them.