Google Trends was announced today, a new service that allows one to compare the evolution of search topics over time. This is the coolest thing I've seen from Google since the launch of their "Google Local" service. Check out some of this examples:

The evolution of the search for the Portuguese cities Lisboa, Porto, Evora, Coimbra, and Faro over time:



The evolution of the search for the Portuguese soccer teams Sporting, Benfica, and Porto over time:



There's a million applications for a service like this, and I imagine this is a great tool for doing research on linguistics.