Arcane Dust and Dream Dust are my big ones. There is a long stretch in leveling enchanting where every recipe takes 10 dream dust, so stacks os 20 go fast. As for Arcane Dust, there are several enchants such as the assault enchants that use only 6-10 arcane dust. These enchants go like crazy so Arcane Dust (which is also used in agility to boots) have a constant sell rate.
In fact, I found a nice secret to skilling up a profession cheaply and still making money off of it. My rogue is a leateherworker and I will find the cheapest green to make that still gives skillups. AH is flooded with them and you get more from the vendor for them. So, I make a million of the one item, send them to my enchanter alt, DE them, then sell the mats for profit. Say I use 20 gold worth of LW mats to skill up on those, I would usually get around 30 gold from the disenchanted mats.
My recent skillup items DEed into Illusion Dust, which made me an insane amount of profit, up around 200% and sometimes over that. So yeah, I would definitely say enchanting mats are good to sell.
Other than that, Thick and Rugged Leather, Silver an Iron Ore (ore usually goes for a lot more than bars on my server), and Scorpid Scales. I used to run around Tanaris farming Scorpid Scales all the time as they sold VERY well on my server. I'd spend an hour farming 2 stacks (was level 45ish), then sell them for 15-17g a stack at the AH.