Now that google has anounced their new Google trends site I couldn't help but mention it. If you spend any type of money at all on SEM you need to check your keywords against this site.
To get a real feel for how important this information will be you should try out a few queries for yourself. Take a simple query like "motorcycle" and then look at the regions tab. A lot of the queries about motorcycles originated from the Philippines. Now look at "pizza", most of the queries there originated from the US. That should make it much easier to target your audience with your advertisments. The trending is nice as well and should give marketers a better idea of when to boost spending to maximize exposure.
This follows another tool Google just release for their AdWords service. You can read more about it at the adwords blog. That tool gives you a different view of the search trends and is more like what you get from Yahoo's advertising system.