The name of the first advertising service for Twitter. Sparq provides a self-service interface that lets advertisers quickly set up the ads. The ads appear on the right-hand column on Twitter as Tweet Now. When someone clicks on the link, it automatically populates the tweet box with the advertiser's message. This can include a link, as well as an option for the user to customize or add to the message.
See "Is Sparq the Future of Twitter?" on InternetNews.com.
See also "Cool Twitter Tools for Better Tweeting" in the Did You Know...? section of Webopedia.