Best places for Humans
There are some places in the game where you can just skin corpses over and over without ever having to kill anything yourself. One of the best places for this on the Alliance side is in Elwynn Forest, the starter zone for Humans. All three of the farms in this zone are literally crawling with boars, and most people who go to the farms for aion kinah will butcher a few pigs on their way through. As a result, there are almost always boar corpses on the ground, abandoned and waiting to be skinned by some enterprising young Alliance player. Your mileage may vary, depending on your server population.
I found some decent tin and sometimes a silver, sometimes, vein under the water in the barren oasis areas and by the thorns that the quill boar camp out at, most notably the quill boars near the south. Usually one tin and one or two copper. There is a mod out there that will remember all of your mining spots and pop them on the map, pushing them to the edge of the map if they are out of range.