Ads on Blogs?

so, I have been working on advertising lately, looking for the cheapest good advertising possible... heh. I've got a few banner exchanges on the website. (only 3 right now, and don't want too many... they rotate, so you only see one at a time, but i don't want people to leave my site, you know?) Then I found some websites that advertise through people's blogs. you choose the blogs to advertise on, and they choose whether to let you. hmmm... but the thing is... Do people click on them? or do they just sit? even if the blog is popular, do people click the ads??? well, I have some up on popular blogs, we'll see what happens.