Real-time web is the next big thing and there are quite a few real-time search services that are creating buzz around. Tweetmeme, OneRiot, Twitscoop, Scoopler etc. Most of these like Tweetmeme and Twitscoop focus around Twitter updates, but OneRiot and Scoopler takes it further to include other services like Digg. Scoopler, which I would really call a "social media search engine" covers Flickr, Youtube, Delicious and other services.
Scoopler keeps it simple and structures the information very effectively. It shows tweets in real-time along with the popular videos, links and images from Youtube, Flickr, Digg etc. Along with it, it also stores your last three searches thereby making it easier to switch between your results.
While your at discovering information through the search, Scoopler makes it easy by showing the entire headline and instead of going to the URL, you can get a "peek" of the content in the target URL and "share" through a host of other services.
More than real-time web I am inclined towards onDemand web as written in the post by @rickmans. With that in mind, Scoopler comes up with too many tweets if you search for a hot topic (Eg: Adam Lambert while American Idol is being aired) and keeps pushing information onto your screen. There is no easy way, time or provision to make sense of the flowing information especially when it is a hot keyword. A "pause" button is critical for Scoopler (or for any real-time service), like in a Tweetmeme or a oneRiot.
Its not eye catchy from a look and feel perspective and I think a lot can be done to improve it.
But, I like Scoopler more than the others right now available.
... and before I finish, Scoopler uses a less known Cloudant, a distributed database service firm (a new type of database) funded by Y Combinator.