From Diablo Wiki
Plans (AKA Designs or Recipes) are objects found in the game that can be used to teach the Artisans new crafting recipes. Plans range from semi-common to extremely rare, and can be found from monster drops or purchased in the Auction House (sold by other players who found them).
- See the Blacksmith or Jeweler page for full details about their respective plans, or the Crafting article for an overview.
Technically, recipes for the Blacksmith are called "Plans" and those for the Jeweler are called "Designs" though most players use those terms, or "recipes" interchangeably.
 Using Plans
To teach an Artisans a plan, simply visit the appropriate Artisan and right click on the plan in your inventory. There are various Achievements associated with teaching them new plans. While the Blacksmith and Jeweler learn most of their recipes as they are trained, most of the higher level or rarer recipes must be taught to them from Plans. The rarest Plans are those that teach the Blacksmith to make legendary items or item sets, all of which are very seldom seen.
 Blacksmith Plans
There are over one hundred Plans to teach the Blacksmith new crafting recipes, and more have been added regularly post-release.
Every base type of item the Smith can craft (i.e. sword, belt, shoulders, one-hand crossbow, etc) has three plans to be found
- Exalted Sovereign: 4 affixes.
- Exalted Fine Sovereign: 5 affixes.
- Exalted Grand Sovereign: 6 affixes.
In addition there are over a dozen plans that teach individual Legendary items or Item sets. These plans are ultra rare, never found by most players, and sold for very high prices on the Auction House.
Additional Blacksmith plans have been added post release, as new recipes and game systems have been included in Diablo 3.
 Jeweler Designs
There are only a few Jeweler designs. At launch there were 4 types of gems and 14 quality levels. The Jeweler learned up to level 11 through training, and required designs to learn levels 12-14. Patch v1.07 added a 15th level of gem, with a new design for each gem type required to teach the Jeweler those upgrades.
- Flawless Star: level 12
- Perfect Star: level 13
- Radiant Star: level 14
- Marquise: level 15
Other Jeweler designs include four types of Hellfire Ring designs, and the Crafted amulet added in v1.07.
A selection of images of plans.
The Staff of Herding.