Bing is the "new kid" when it comes to search engines. I'll be the first to admit that I haven't used it much, partially because I'm happy enough with Google and partially because Bing keeps getting confused about my location. (Some of the time it think I'm in the UK, other times it knows I'm in Ireland)
In any case Bing (Microsoft) have done some kind of deal with Twitter to offer more of a "realtime" search experience.
The new Twitter service on Bing was launched in the last couple of hours, so it's brand new.
What's cool about it is that gives you tweets + links.
So a search for "ireland" will give you the latest "tweets" (messages posted on Twitter) followed by the most recent links associated with the keyword. So if you post a link to something cool on Twitter it should be picked up almost instantly and "ranked" against the rest of the community.
Danny Sullivan has posted in more detail over on SearchEngineLand. Hopefully Bing / Twitter won't be swamped by the spammy junk that can get sent onto Twitter by automated scripts...