This is interesting -- I had no idea they were doing it, anyway. Apparently Curse Gaming has been running a weekly story where they post the median global sale prices (from WoWEcon) on all sorts of high-selling commodities. It's a nice read, and helps me get a feel for how my server is compared to the global average, as well as giving me a touchstone for how to price things.
It's broken down into categories, like flasks, food, recipes, trade goods, etc. There aren't a lot of surprises on the list (well, I spend a fair amount of time at the AH, so that might just be me). Mage books top the spellbook list, as always -- why is that? Perhaps it's because mage books teach new ranks of core spells like Conjure Water, whereas other classes' books just tend to teach group versions of buffs; you can get by longer without those. There's an interesting discrepancy between Fel Armaments, at around 20g, and Arcane Tomes, at about 17g. I guess Aldor is more popular than Scryer. Fel Iron is worth considerably more on my server than usual, though most other prices are about in line.
In the recipes section, it looks like Blacksmithing has the most in-demand stuff -- people are paying 1200g for Plans: Dirge, and 1000g for three other plans. None of the other professions have any recipes that high. Anyway, go check out the full list over at Curse -- it's pretty neat, and has coloring depicting whether the price of an item has risen or fallen since the previous week. Thanks, Curse people, this is a nice resource.