Twitter started serving third party ads using a small box on profile pages. But all these ads are about twitter and its apps. I do not whether twitter will serve ads not related to twitter world. As it is serving twitter aps, and twitter clients it will useful for users. Do you know how to put your add on twitter and how much they charge? please tweet me at digisteps if you know.

The above graphic show you ad placement (marked by arrow). Ads are displaying only on profile pages.