I really liked Adbrite when it first came out but now it seems that most of their clients have moved away from selling ad space for a fixed price. Basically, I want to buy ad space on busy websites for a fixed price and want to keep away from PPC or CPM. Please let me know if you know of any good ones.
If I can squeeze in a little self promotion for my company, TextAdMarket (see sig) We sell ads based on "per day" rates rather than actions, clicks or impressions. You also get to choose how long you want to advertise for. We are a new company, however, so our ad network is small but growing. Give us a try! The reason I started the company, is because there aren't too many link brokers who sell on a "per day" rate. I've been doing that as both a publisher and an advertise for roughly 7 years now, and it has never let me down.
Adbrite is a pain sometimes but there they have been a recent decrease in alot of ppl earnings recently. I guess its just a phase or something.
When I first used Adbrite most of their ads were at fixed prices for a set amount of time. Now it seems like they're trying to be more like Google Adwords which is probably the wrong way to go for their company.
you should look at text-link-ads - make sure you sign up for ads on decent alexa ratings else you might not get too many visitors