I thought I'd add WFG's stats to this discussion, for the sake of balance.
In the last two weeks, nearly 2/3 of our traffic came in direct or via search engines on our name and aggregation services (ie. people who already knew about us).
In terms of listed sites, the top referrers are Eli's site (novelr.com), my site (courage-my-friend.org), srsuleski.com (Queen of Seven, Alisiyad, Dreamers), skyladawncameron.com (Catharsis and Children of the Apocalypse), millvexations.com (Mill Avenue Vexations), and illisemontoya.blogspot.com (Eikasia). We seldom get more than one click per day from any other listed website, and (something I found very surprising, as we aren't presently advertising there) we get more referrals from pagesunbound.com than any one of the vast majority of our listed websites.
At this point, we aren't advertising -- the money has already been spent. We depend on you guys for both readers and our page rank in Google. Part of the reason we don't have more traffic for you guys is we are four pages into Google's search results for "online novels", which is the high value search term providing some of you with traffic from onlinenovels.net and free-online-novels.com (at least one of which charges a monthly fee for listings). We've already done just about everything we can to improve that page rank (we've moved up 4 pages due to those changes). What we need now is for more people to link to us with the words "online novels" in the link label. Failing that, we'll have to start advertising again, and 300 000 impressions last time only increased our readership by about 50 readers a week, so that's not an option we can really make work.