Is there way to see where certain herbs and ores have been found in the past? Like if someone in my guild says, hey where should I go to mine lots of "insert ore/herb here". Can I do something with Gatherer to look and tell them, oh yes, looks like I found a lot "insert good place to mine/herb"?
Sure, enter in the name of the herb in the box at the top of the report frame.
That will then show the list of where you found the goodies, you can then sort the list on location, et cetera.
Once you know the location, depending upon how many items are there, you could then, also, select only the given herb/ore in the Configuration and then look at the maps to see exact locations in the specific zone/subzone.
Out of game, the best resource is likely our friends at http://Wowhead.Com - there, you can search for specific herbs/ores and then see on the maps which place has the most and their locations on the maps.