Microsoft has had a search engine for a while, and it just doesn't compete with Google - not that much does these days. They've decided to repackage their existing MSN and Live search tools in to a new tool with a new name: Microsoft Bing.
They feel like they'll be able to compete with Google for ad revenue with this change.
I took a quick look - it has a nice look, and they stole the "simple" approach from Google. Instead of a hugely cluttered page, it's much simpler than before, and I like the "Popular Now" feature. I did a few searches, and Google still came out ahead in terms of finding what I want. However, this might be something that gets them some attention. I'd encourage you to check it out, if nothing else!
Story about Bing