I am running a quite niche blog with very few competition from other bloggers in this industry. I get about 1000 unique visitors a day and display Adsense adverts on it. I would however prefer more targeted image banner advertising for a lot more that I am getting for my web real estate from Adsense (at least for the image ad section). Does anybody know what sort of companies help in with sourcing dedicated advertising clients? Or is it an activity I'll have to conduct myself?