Twitseeker - search for people based on what they tweet about
If you want to know how popular you are based on retweets checkout Retweet Rank
Bubbletweet - create a hosted video message, and then tweet the URL to your stream, so your tweeps can see your video, or put the URL into your bio.
You cannot embed the video onto your actual Twitter profile, instead a bubbletweet version of your Twitter profile, see Marshall’s.
Free Twitter Designer