I have quite a few Tumblr blogs, and for a long time I've only monetized them by making posts that link to a monetization site. This works really well, but I'm starting to get thousands of visitors going to my actual Tumblr blogs that I'm not monetizing. I tried Chitika Ads, and they are awful. Even with placements that bring in decent CTR, my CPM is just pennies. I don't want to risk my Adsense account, but has anyone found a decent ad network for Tumblr blogs?