Do you Twitter? Even if you don’t use it, you’ve probably heard of it – part micro-blogging platform, part social network, part self promotion tool. Some Twitterers boast followers (people plugged into their Twitter network) in the thousands. It was only a matter of time before someone figured out how to capitalize on the service’s popularity.

Now you can purchase advertising space on Twitter profile pages with a service called TwittAd . TwittAd gives Twitterers the opportunity to monetize their empty backgrounds and advertisers an “in” with the popular social service. They system is simple to navigate for both parties. Twitter users list their real estate on TwittAd, specify the number of “followers” they have (the real bartering chip here), and set their price. Advertisers purchase space at will and upload their ad within 24 hours of purchase. Users can accept the ad or deny the transaction; if accepted, TwittAd takes a 5% commission on the sale.

For the most part, TwittAds are unobtrusive, occupying only a portion of the left side of a user’s profile page. Considering most spaces sell for a couple of bucks (with lifecycles ranging from 1 day to 3 months) you can afford to experiment.