I joined Adgitize yesterday. I read about this program a few weeks ago, but there was one thing I didn't like: you couldn't control who advertised on your blog. Note the past tense--that has changed now, and you have the option of rejecting certain ads.
Adgitize is kind of like Entrecard, except you can earn money through it (not just credits). You can also put more than one ad on your blog, which allows you to double (or triple, or quadruple) your credits earned--very helpful for lower traffic blogs.
I went ahead and paid for a month's worth of advertising for one of my blogs. It gave me results pretty quickly. Here's a picture of my statcounter stats:
I'm really interested to see how this turns out. I'll write a more thorough review after a few weeks, but so far, so good! It was really simple to sign up and get their codes.
If you're interested in joining, please use this link and put a few pennies in my pocket: