Google has done it again, with Google Calculator. Want to know what a mathematical expression evaluates to? Ask Google: 7 * 11 * 13. It can do it with words too: two plus two. Units of measurement are no problem: radius of earth in miles or speed of light in furlongs per fortnight.
The thing that amazes me about this is not how useful it is, but how Google has implemented it as part of their standard search. To make this work, they have to sniff out calculations in search terms. This determination comes up with yes, no, and maybe. You can see this based on whether Google gives you search results (gram), calcuation results (pound in grams), or both (pound). Because Calculator is not a separate page, but a regular search query interpreted differently, Google has to run this calculation sniffer on every search.
I know Google has an enormous server farm devoted to making searching fast, but to have that much confidence in a new feature, and one that will only kick in occasionally, is inspiring. Lesser developers would have moved this off to a new page to protect their baby, but would have had a less useful feature. The cool thing about Calculator is not that I as a geek can go to Google knowing that it will do a calculation. The cool thing is that ordinary people who don't know any better will get the answer to their question.
As it happens, about a month ago, I really did want to know about tablespoons in a cup. I typed a query into Google to get the answer. If Calculator had kicked in and showed it to me "magically", I would have fallen out of my chair and made offerings to the Google gods. Of course, in the final irony, being a geek, I knew that "in a" were useless words in a search query, and searched on tablespoon cup conversion, which doesn't invoke the magic of Calculator.