Quick note I got Wowhead Tooltips working so I will not be bothering to explain what any items do anymore.
Blacksmithing has the same basic layout as Wrath. It doesn't however have all the complexity due to Cataclysm only having 5 levels to work with. Also there are only a few pieces of armor any blacksmith will be crafting to gear for level 85 Heroics and raids. I do not believe any of the low level gear will sell well right off the bat in Cataclysm and so at least at first to make Blacksmithing as profitable as possible you will need access to the later patterns.
First off are the consumables. Elementium Rods will be very popular with all the enchanters that will be forced to buy them. I would expect to make a good amount of gold off these early but as more competition enters the arena expect to either lower your threshold considerably or wait for the Alt army to begin leveling additional toons before selling these as often.
Elementium Shield Spike and Pyrium Shield Spike will both be popular. Elementium for leveling tanks and Pyrium will be popular for both Tanking and Prot PvP. Pyrium Weapon Chain may prove to be valuable as well although I do not believe they will carry the same demand as the shield spikes.
Of all the consumables the Ebonsteel Belt Buckle will, by far, be king. Even today I'm still selling 15 to 20 Belt buckles a day. Even with a large number of competitors this belt buckle will provide a good amount of income through out the expansion.
Next is the End game gear. Apart from a few Epic pieces or armor and weapons people will not be looking to you for Dungeon and Raid gear at 85. If you happen to have a good sized PvP population on your server however expect a large number of sales early in Cataclysm with the Bloodied and Ornate PvP sets. Wile Bloodied will heavily outweigh Ornate in sales numbers don't shun it completely as Holy Paladins will be able to do decent spell damage on top of their heals making them great for PvP.
Outside of PvP gear every end game piece requires Chaos Orbs. with blue weapons and shield requiring 1, the epic Chests 3, and Belts 2. Notice that they these Orbs are BoP. This will allow Blacksmiths to completely control the market. No more of someone gathering all the mats and finding someone to craft for them. Even if people do ask you will be able to charge a fee for crafting and your Orbs. Although I'm not looking forward to all my guildies expecting me to use my Orbs to make them items for cheap. Wile this may push more Blacksmiths into the Epic market as they amass Chaos Orbs faster expect to see high percentage margins at first and possibly see them return with the start of each raid tier.
Leveling Gear: I do not believe outside a few pieces that leveling gear will be worth selling at first. A few weeks into Cataclysm however and some of the Altoholics will start bringing up toons that are not geared up at 80 and so will greatly benefit from some of these pieces.
for level 81 there are rare weapons. Included is a 2h sword, an agi dagger, a spell dagger, a agi axe, a polearm, and a healing mace. Expect these to sell well as they will be replacing heirloom weapons that do not increase after level 80. In that same boat I would expect the Chest and Shoulders from the Redsteel Dps set and the Stormforged healing set to sell well. Wile other pieces from these sets may sell they will not sell as often as these shoulders and their respective chests.
Anyone who is a big fan of selling the Cobalt tank gear will be a fan of this next item set. The Hardened Obsidium Tanking set Consisting of Helm, Shoulder, Chest, Belt, Legs, Boots, Wrist, Hands, and Shield will be popular. Short of a few items potentially substituted by early quest rewards I would expect every part of this to sell. Sales my be slow at first but I believe with the alt mentality most players have developed there will be enough tanks leveling through out the expansion to make this set worth your wile.
And that Wraps up Blacksmithing. Skipping to Engineering tomorrow as Enchanting relies to much on crunching numbers to determine which enchant is best. Also Enchanting doesn't provide enough variety at first for any of the high end cata enchants not to sell. And wile Engineering still isn't a major money maker it has been provided with a few extras in cataclysm capable of making a good amount of gold.