http://qcl.me is my pet project and it is starting to get attention, I get between 40 - 50 uniques a day, and some times even up to 80. I am working on marketing it more and people are adopting it quickly.
So for one day it will cost 0.001 Bitcoins. If you want multiple days just say 3 @ 0.001 =0.003
Get on the ground floor cause next month it could be a lot more for ad space.
Btw this is only the second month it has been running.
Ad format can be html or an image, I host for you, it will cost extra if I have to host the image for you, it will be 0.0005 extra.