Twazzup, which just launched this morning, tries to bridge the gap between Twitter's real-time search and a more traditional search engine. While Twitter's real-time search is great for keeping an eye on current developments, it is not a great tool for seeing which links about a given topic are currently popular. On Twazzup, you can follow a real-time stream of updates including a certain keyword on the left, while the right sidebar shows the top tweets and a list of the top tweeted stories about this topic, as well as related photos from twitpic.
One of the most interesting aspects of Twazzup is that it also displays a list of the most authoritative Twitter users who have tweeted about a given subject. This should allow Twazzup's users to quickly find interesting users who might be worth following.
In addition, Twazzup also allows you to easily restrict your searches through lists of related keywords and sub-trends.
Of course, Twazzup is entering into a rather crowded market. Oneriot, for example, just launched an alternative Twitter search engine that focuses on links, and services like MicroPlaza are trying to give users personalized Twitter meme trackers.
Thanks to its clever mix of real-time search and top-tweets, however, Twazzup offers a lot of functions that its competitors can't currently match. It would be great if we could also specify persistent searches on Twazzup, and some of the top tweets and related photos sometimes seem a bit off, but for a first public release, Twazzup already provides a lot of functionality and the team will surely improve upon this in the future.