People who are interested in a certain subject matter are all on a ping list. It's totally user-run. For example, I am on the list called the, "Puff List." The threads about smoking and tobacco are noticed, or posted, by a FReeper who keeps the Puff List, and they reply to the thread with a list of names which they sometimes have saved on their hard drives in WORD format, or something similar.
There's an old listing I saved in my links.
Here it is. it lists a bunch of lists.