With the holidays over and adults/kids returning to their normal routine I predict a huge change in the prices of mostly all crafting material. Blizzard created a critical intersection by releasing Cataclysm before the holidays and this will benefit you if you act fast. Over the holidays children were on break so they basically stayed up all night, woke up early, and farmed in Cataclysm. So for almost two weeks the prices for farmable mats have been relatively low. Like mostly all guilds on all servers, my guild has waited until the holidays were over to start raiding. When guilds start really raiding the mighty balls of pugs grow and more start to form. For any pug to have a shred of potential they will need higher enchants, higher gems, higher gear, and tons of flasks.
To start it out, all of the Christmas vacation kids are going back to school so less and less mats will show up on the auction house. Then the raiders/puggers intersect that, creating a demand that is much greater than the supply. To meet market equilibrium the price has to rise.
It only makes sense that you should invest in low cost materials before the small stockpiles from the holidays dry up. The main materials I am going to focus on are for flasks, enchants, and belt buckles. you may have noticed that really none of these items have been selling and that's because there was very little need. Most players that have a bit of gold dont want to blow it on a belt buckle just to add one gem, for their heroics... but once the raiding kicks in every bit helps and they will realize that after their first 20 wipes. Most guilds also aren't investing much into flasks, or so i've seen, so anyone not wanting to look like a fool in their guild raid will be buying flasks.
Like i said here are the mats for the belt buckles that i expect to go up in price along with its mats.
Ebonsteel Belt Buckle:
4 Volatile Earth
4 Elementium Bar (8 Elementium Ore)
4 Pyrium Bar (8 Pyrite Ore)
I would invest in abnormally cheap herbs of all kinds, Cataclysm enchanting mats, and the mats listed above for belt buckles. With the rise in price for herbs you can expect all items relating to the milling of them to rise as well... mysterious fortune card maybe...