I am going to give blogging advertising network Adgitize a try. If you are familiar with Entrecard, it looks like Adgitize has taken some similar ideas and expanded upon it by adding an affiliate component, as well as the ability to pay for ads on their network on a monthly basis. The price for one month of ads on blogs all over the network is just $14.00, or you can try it out with a 7 day ad for just $7.00 or 14 days for $10.00. It's a low cost way to advertise your blog. Blog writers can get points for writing blog posts as well as from clicking on the ad on other bloggers blogs, so you can get some blog traffic this way. (Although a lot of the traffic might be "drop by and run" quick hits)
I am planning a blog redesign for Marianne's Motifs, so this might be a good time to try Adgitize. I have a little bit of sidebar room to spare for a 125x125 ad. Here's an example of what the ad might look like.
I think this guy has a great idea in that he is charging a reasonable fee for the ability to advertise on lots and lots of blogs. I haven't wanted to pay the money to advertise with AdWords from Google because they expect you to start at paying about $50. But I think I could get my feet wet with $14.00.