The mod you are looking for is called Gatherer and it is hands-down one of the best and most usefull add-ons ever made.
You can find it
here
Not only does it record the location of any herb/ore node that you click on and mark that location on your mini and main maps, it also shares these locations w/ members of your group, raid and guild and vice-versa. So if you can get some, or even all, of your guild-mates to use Gatherer you'll quickly find that you have thousands upon thousands of marked node locations to aid in your gathering. Like I said, Gatherer is one of the best, and most usefull mods I have ever used.