Just off the top of my head;
Red Ridge had some good tin deposits. If you need tin, head there. However, at your level you're probably itching to get into Iron (125 skill). Go to the spider cave just at the beginning of the Wetlands (if you come out of the tunnels from Loch Modan). There is a type of deposit in there for an ally quest, but it'll push you to 125 no problem.
Once you can get iron, I suggest heading over to Thousand Needles. Make a circuit, and be sure to run around the edges of the map. Hit the wyvern roost area (2 iron spawns), the harpy cave (2-3 iron spawns), circle around the Shimmering Flats (2 spawns of iron, some tin/copper), and go through the caves in the centaur camp (2 spawns). Along the way you should find 4-5 more iron spawns, and lots of tin/copper. There is also mithril in the caves, but you're too low for it.
Once you get up to the mithril level, you have a lot of options with a few nodes. Try looking in silithid areas; the one in 1k Needles often has two nodes, as does the one in Feralas. Tanaris has a lot of mithril, but it seems to be quite spread out. Skulk Rock in the Hinterlands has some nodes, and running around the edges of the zone will get you more. Mithril is plentiful, and lasts you for a long time.
When you get to Thorium, I found Un'Goro to be nice (again, the silithid hive has steady nodes). Azshara also has a lot of mithril and some thorium.
When you reach Rich Thorium, I hear that EPL has a great circuit, and Winterspring has some nodes. However, the best locations will be ooze-covered rich deposits in the elite bug hives in Silithus. As you can stealth (lucky bugger), it should be easy to hit each hive, find the nodes, and get out.