I mentioned Wolfram|Alpha the other day but I was a little slack in doing nothing more than linking to it. And as Bonus quite rightly pointed out in the comments it’s not intended to replace Google. Or at least not totally.
It’s not intended as the place to go when you are after gossips, news, opinion, websites addresses or just have a vague question about something. It’s for when you want the cold hard facts. Unlike most search engines it pulls data in from various sites and creates a database of knowledge. At the moment it is a rather lightweight database but it does make it a very good tool for getting answers to those specific questions.
What percentage of traffic it might steal from Google really depends on how quickly it can fill it’s database and what percentage of search traffic is after the sort of answers it returns anyway. Google are also close to launching ‘Google Squared’ which will (apparently) be similar but try and create a database out of the information available on the whole web rather than specifically selected sites.
Wait and see where things go I guess but my money is on Google getting there first.