Vein miner, NEI, Better Builders Wands, Waila, Damage Indicators, Durability Show, and even Inventory Tweaks. All of these are really useful for the average minecraft player and world
Technically none of these mods seem able to be used as cheating all they do is let you mine multiple blocks at once, shows you recipies what you are looking at, mob health and they let you see your durability of tools and armor, and InvTweaks just lets you rearrange your inventory and chests easily