I've found that fast traveling between blacksmiths as they restock is much more efficient than mining as a method of leveling smithing.  Ore veins are few and far between and as far as I know, the respawn time is when the area resets. Furthermore, the act of smelting does not by itself give you experience.

For that reason, I found bouncing between War Maiden's in Whiterun, Alvor in Riverwood and Beirand in Solitude, buying their entire stock of usable ore, ingots and leather, turning it into weapons or armor then selling those back to them was the fastest method.

Since you gain experience in smithing proportional to the value of the items you create, there are a few items that can make the process more efficient.  Those are the [Forgemaster Fingers][1] and the [Notched Pickaxe][2].  You can use the enchantments on these items to improve the items you create beyond you current skill level.

I also found that for each type of item you can create (Orcish, Elven, etc.) there is an item with the highest input to value ratio.  If you are going to grind smithing, it is best to grind whatever item this is for your level.  You can refer to the tables on the relevant type. For instance, for [Dwarven smithing][3], the bow has by far the highest ratio as it requires only two dwarven ingots and an iron ingot.


  [1]: http://www.uesp.net/wiki/Skyrim:The_Forgemaster%27s_Fingers
  [2]: http://www.uesp.net/wiki/Skyrim:Notched_Pickaxe#Notched_Pickaxe
  [3]: http://www.uesp.net/wiki/Skyrim:Dwarven_Smithing#Dwarven_Smithing