Google Insights for Search allows you to compare search volume patterns across regions, categories, time and more. Go to http://www.google.com/insights/search/# to get started.
The following screen shows how you can narrow down your data:
Here’s an example of a Location Search. We’ve chosen the UK and England as our location. We’ve chosen “Web Search” (as opposed images, news or products) and “iphone 4” as the keyword tool. We’ve also chosen searches in the last 12 months and kept the default of “All Categories”.
The results include a graph mapping the interest over the chosen time period. It also shows the most popular categories.
The tool also breaks down the interest into smaller regions. You can view that information in text:
Or on a map:
It also shows you the popular search terms:
And finally, it shows you searches that are on the rise:
You can choose to embed either of the 2 search term tables to your website. Just click the “Embed This Table” and follow the instructions: