After spending some time browsing this thread to find some new advertising networks I could try out, I realized that there isn't a thread with a comprehensive list of ad networks (if there is I haven't found it... yet).
So how about we create a list of all the ad networks available to make it easier to find. Feel free to add to the list.
This list doesn't differentiate between good/bad networks. It's just there to provide publishers a starting point for companies they might want to explore the possibilities of. Of course I would only suggest that you use the first tier networks, or at least do some extensive research before entrusting your inventory to a company.
Cost per click - the cost or cost-equivalent paid per click-through.
Yahoo Publisher Network [NOW CLOSED]
Cost per thousand impressions
Buds Ad Network
24/7 Real Media
Mamma Media Solutions
Ad pepper Media
Cost per Action - model in which payment is based solely on qualifying actions such as sales or registrations.