Google Flight Search
Internally, this has been around for a little while (disclaimer: I work for Google but not on anything related to this).<p>What continues to impress me about Google is:<p>1. Just how quickly this was built (really, it was quick); and<p>2. Google wants you to use our services because they're compelling not because we don't give you any other choice (ie "Don't be evil").<p>Sure there are limits to what it currently does but I think you'll see it rapidly iterate.