www.wolframalpha.com (//http://)
And times online explains why:
http://business.timesonline.co.uk/tol/business/industry_sectors/technology/article6307744.ece (http://business.timesonline.co.uk/tol/business/industry_sectors/technology/article6307744.ece)
It's a bit limited, anyone suggestions for fun things to do besides checking my own birthday and town?