Similar items to peacebloom that are profitable on most servers for people getting started include: Hypnotic dust, Celestial Essences, Relics of Ulduar (and other rep items), and heavenly shards. The same can be said with the earlier wrath enchanting mats, they are still valuable for casual players or those without a lot of disposable income! This list is not the end all be all of making quick money! Check your scan results daily and add to this list and you will be on your way to hitting the gold cap much faster than those who quest or farm!
While this is more a method than a farm, I still thought it belonged in this video.  This method takes advantage of the long forgotten spell, void shatter.  Generally because of the logistics behind how easily obtainable void crystals are when compared to large prismatic shards, void crystals cost SUBSTANTIALLY less.  The void shatter spell however turns 1 void crystal into 2 large prismatic shards.  Globally large prismatic shards are worth 15g a piece, while void crystals trend around 2-4g a piece.  Can you do the math on that?  You can literally triple your investment cost by creating more prismatic shards for your market.  All it requires is for you to get honored with the shattered sun offensive, a little known fact that most enchanters are too lazy to take advantage of.  Nobody is doing this, and on most servers the market it ripe to take over.  Don't believe me?  Check it out yourself!

Bags: This SHOULD be a no-brainer. The cheap-o version are Netherweave bags, but if you have the gold I recommend you get the largest bags you can afford, since it means you won't have to stop to clean them out as often. In fact, if you have an excess of gold, it's probably not even worth your time to stop and loot mobs that aren't quest objectives. This seems like a small thing, but over the course of 100+ levels, all those clicks to loot add up.
Many players who already have higher level characters create alts that they level to a certain point and then stop. Often, these twinks are level 18-19, 28-29, 38-39, etc. for the purpose of going to battlegrounds at the top of their tiers and kicking butt. Since these twinked characters are owned by higher level players with lots of cash, they usually outfit them with the best gear available at their level. Thus, items that require level 17-19, level 27-29, or any other items around this level, with good stats or dps, often sell for much higher prices than they normally would. This is especially true on an older server, and also especially true of blue (rare) items. In general, "good stats" include Cloth "of the Eagle" (for mages, warlocks), Leather "of the Monkey" (for hunters and rogues), and Mail "of the Bear" (for warriors/paladins)as well as weapons with these suffixes that can be used by the right class.
The most simple thing is TradeSkillMaster. This AddOn shows you quite an amount of information in the items tooltip. In my opinion, DBRegionMarketAvg the best source. It tells me the price, an item was posted on all EU realms in the last 14 days. Why not DBMarket? DBMarket only shows you the items value from your server in the last 14 days. This value often gets manipulated. Some people start to post an item with a 500g value for 500.000 Gold on the auction house for several weaks. As a consequence, DBMarket is rising towards 500.000 Gold.  If you use DBMarket with 100% and post your item for 500.000 Gold, nobody will buy it.