Last updated: 21 Dec 2010 - This is a work in progress!
When Deathwing roasted Azeroth, he left fiery destruction in his wake. The volcanoes, tidal waves and rents in the crust thrust different metals to the surface, while melting others clean away.
I have now updated my Mining charts, showing the post-Shattering zones where ores can now be mined. The current version was created using current spawn count stats from Wowhead. It will be updated again in a couple of weeks once the stats get a little more mature.
Mining 1 - 300 & Outland:
Click the chart to make it bigger
Mining in Northrend and Cataclysm zones:
How to use the charts
The number in each box is the number of nodes of metal that spawn in in each zone, based on data from wowhead.com. I have put an asterisk in the starter area boxes because there are a LOT of nodes in each of these zones.
Look at the metals that you are able to mine at your current level of mining. Where do those veins spawn the most? Where does the next level of ore spawn, and what level do you need before you can mine it?
For example, if your mining is currently at 79, you can currently mine Tin, and combine it with Copper to make Bronze. Smelting Tin goes grey at 75 so you won't get more levels from smelting Tin, but Bronze isn't gray until 115, so you could mine more Copper and Tin and make Bronze out of it. Iron isn't available until 125, so you're either going to have to hang around in Ashenvale or other areas spawning Tin until you get up to 125, or come back and do it later.
Once you get to Outlands, keep in mind that you need to have at least 350 mining to start your Northrend gathering, so pick up any Fel Iron you see.
Mining Obsidian starts at 425. On Wowhead at present no counts are showing for Mount Hyjal, but commenters report that there are indeed plenty of nodes there. There seems to be an issue with phasing, similar to that experienced in Icecrown, where you can see nodes on your map but they are not in your phase so unable to be gathered. I'll try to update this in a few weeks if the issues have been worked out.
Note that Dark Iron is now only available within Molten Core and Blackrock Depths.
There is one last thing that I can't help you with, and that's that you must remember to train the next level of Mining before levels 75, 150, 225, 300, 375 and 450!
Please feel free to comment with any suggestions for improvements for the charts, or to tell me if you found it useful!
EDIT: I have created another chart showing the gems that can be mined and prospected from ore. You can find it here. It is not yet updated for Cataclysmic ores.