atladsenser - 3:28 am on Oct 6, 2011 (gmt 0)
I've tried both Kontera and Vibrant Media. Though they aren't contextual ad networks in the same way that AdSense is, they are additional ad networks you can try.
I know many publishers have had the opposite experience from me, but I've had much better results with Kontera than with Vibrant. I think it's just the advertiser mix that Kontera has vs. what Vibrant has -- they're more suited to my site and audience.