- on http://celebritytweetarchive.com/ users can leave comments under tweets - also seen on tweetmeme. If you can get people commenting, that'd be massive.
- there isn't a twitter account to follow with the submissions. Then place an additional link back the comments page in those tweets.
- have user icons
- count submission points by the number of rewteets made on site, and generally by the site's users off-site, or just number of retweets (or an upvote)
- you could just create a generic 'digg for tweets' - then have a bookmarklet that a person clicks when viewing a single tweet to submit the tweet, or toggle into the site.
- perhaps when a tweet is submitted, it becomes a favorite, or when it is favorited, it is submitted.
- split the site into different sections, eg see http://favstar.fm