As many have reported and probably read, 4.0.3a has shaken up the markets a bit with changes to drop rates on formerly rare recipes and items. An example of this would be Recipe: Savory Deviate Delight, which was a rare drop in the Barrens, but now drops fairly frequently.
I've also noticed the drop rate of uncommon items has increased during some achievement farming. I did a quest chain in Darkshore to obtain Withers a new non-combat pet, if you are horde you do not have to do the quest line. If you're Alliance, you to Darkshore and pick up a quest near the flight master. You go on a pretty epic journey saving Nightelves and gathering reagents, saving a bear, and eventually fighting against the Darkspear trolls before being sent back to the new Darkshore Alliance quest hub, Lor'Danel, and receiving your pet.
If you haven't tried out "Peacebloom vs Ghoul", especially if you are a fan of Plants Vs Zombies, head up to Hillsbrad, just south of the Dalaran crater. Once you work your way through the short quest chain and defeat the end boss, you get Singing Sunflower.
Also, I've been working on Wintersaber reputation, and I've noticed the drop rates for the provisions quest is about 90% now, I'm getting tons of uncommon items. However, the Furblog mobs you need to kill seem to be fewer, perhaps it's worth trying to farm in other places? Also, you can't get to the appropriate giants without the use of a flying mount, or jumping to your death and taking rez sickness to revive on the other side of the gorge. The mobs are located right outside the gates of Hyjal, a bad placement, but only a temporary inconvenience.
On to some gold maybe?
Yea, there's not much to say here, really. Glyphs are selling alright, prices seem to be going up slightly, but it does seem that a few of the serious glyphers picked up on the ink changes, although I have seen a fair bit of rage and QQing in trade.
Herb prices haven't really dropped much, if anything there's fewer herbs than ever on the auction house, so no stock-piling herbs for me. However, saronite keeps dropping in price. Gems have increased in price.
My opinion, is that right now, it's best to not freak out and dump items, they WILL sell... eventually. Just horde away anything that won't sell now, don't buy anything unless it's a safe buy, aka : vendor price, or high demand leveling material. Check out any Cataclysm profession guides to get an idea of materials that might not be used any more or as much for lower levels.
Otherwise, really, go and enjoy the game before you're up to your eyeballs in farming, power-leveling and fresh 80+ content.