There’s an easy-to-use addon called “Lil’ Spark’ys Workshop” that lets you find profitable recipes that you have.
It calculates cost of materials based on either Auction House or Vendor prices (or can pick the best of the two). It adds up the cost of all the materials and then compares it to the Auction House sale value of the crafted item. It flags items that can be crafted and sold for a profit.
Obviously this requires that you also have an auction house mod that captures average prices. It can use the AH prices from Auctioneer, AuctionLite, AuctionMaster or Auctionator. As long as you have one of those, it can correctly identify profitable recipes.
You can download the addon at curse.com: Lil Sparky’s Workshop