The OneRiot RiotWise Ad API might be right for you: http://oneriotdevelopernetwork.com/riotwise-api/ http://oneriotdevelopernetwork.com/riotwise-api/ You have

The OneRiot RiotWise Ad API might be right for you: http://oneriotdevelopernetwork.com/riotwise-api/ http://oneriotdevelopernetwork.com/riotwise-api/ You have the option of text ads (typically trending news stories, so they're less spammy than typical ads), small display ads, or full ad units. Additionally, OneRiot's whole approach is real-time/trending information, so it's well within the Twitter-ish sphere. I have some friends who have used it and reported good CTR and positive (or non-negative) user reactions to the ads.