I came across an interesting post on TechCrunch that mentions how Twitter has begun to advertise applications (most of which are all Twitter-related) earlier this month. Some of the links being provided in small boxes on the profile pages are Tweetie, Twittervision, and ExecTweets. Even though developers are not yet paying anything to get featured on the site, it will be interesting to see how Twitter will respond to paid advertising on their site.