One other web comic site (I don't know if I should mention it) uses ProjectWonderful.com to let it's members (or anyone for that matter) advertise on the site at the bottom of all pages. It runs small-small ads across the bottom and the cost isn't too bad. People can click on it and go whereever you make it go (like you website home page, current comic or the start of your comic, etc. etc). It's an inexpensive way to advertise and DrunkDuck get pocket change to boot...