A user on Quora asked "Are there any free or cheap tools that would enable me to monitor a keyword and be notified whenever somebody over a certain follower threshold (say, 100,000) used it in a tweet?" I thought it was a great idea, so I built it. Specify Twitter keywords, set a minimum follower count, and receive an email when a suitably popular account tweets about it. You can also exclude retweets and filter out chosen accounts.
Picflood presents an unfiltered stream of pictures publicly posted to Twitter, updated in real time, with or without a filter for text in the tweet. Because of the specific Twitter API stream that Picflood hooks into, users see only a small subset of Twitter photos, but they still come through fast enough that it's hard to fully process each image before it disappears. Very NSFW.