In dealing with the scorching hot economy at the beginning of the Cataclysm expansion, there is an easy way to make a lot of gold : reassemble odd-shaped stacks of products into the standardized stacks of 20. For some reason, players seem to think that adding 150 individually priced herbs or ores to the market is a good plan. At this point in the expansion, it isn't. Maybe a few months down the line (or, occasionally on specific items for specific reasons), breaking stacks down to individual components can be profitable. But right now the big spenders are spending. And what do the big spenders value? They tend to value their *time* as much as anything else, and many are willing to pay a significant premium to buy in stacks instead of individual (or other odd-shaped quantities).
The best market to take advantage right now is the Volatile Earth/Fire/Water/Life/Air market. Scoop up the 100 individually priced Volatile Fire that are selling at 15 gold a piece and put them in stacks of 20 for 450 gold a stack. That's a 50% mark-up, and players are willing to pay it. This applies to all tradeskill items. There is a ravenous demand for them, and getting a large quantity of them at a reasonable price quickly is just as important to many players as finding the absolute lowest price. Also, most players don't use Auctioneer and most people are terrible at math. Make your stacks look "close enough" to the individually priced items and you'll lure in the non-mathletes along with the streamliners.
When buying many individually priced items, be sure to use Auctioneer's snatch feature. It turns three clicks in different spots into one click in the same spot(when you use the ctrl-alt-shift command when clicking the purchase button -- though, this is sometimes buggy, which can be fixed by simply clicking to one of the other search functions in Auctioneer like "resale" and then back to snatch again). This adds up to heaps of time and energy when purchasing large quantities of commodities.