Trends in search marketing are changing as market demands change and new consumers enter the space to use the medium.  It is important to be able to these research trends and track them relative to our campaigns so as trends emerge, we as marketers can leverage them. Among other subscription tools, Google's free Insights for Search tracks keyword trends over time, giving marketers the advantage of knowing what people are searching at any given time.  Marketers can leverage this information to improve the effectiveness of their search marketing campaigns. Take a look at this example comparing searches for Ford, Honda and Toyota throughout 2007 and 2008.
The graph below shows searches for Honda peaking around June of 2008, probably in part due to the brand's perceived fuel efficiency during a time of record gas prices.
Also noteworthy is the ability to compare keywords geographically.  Using this chart, you can see that the highest concentration of Honda searches comes our state of North Carolina. The reasons for the different trends can be speculated based on keyword intent, however the results can be extremely helpful to online marketers.  Using this fee tool you can quickly better understand search queries relative to others and geographical interest.  Our clients rely on us to generate strong return on marketing investment; we leverage research tools like this to help.  Bookmark this site for free keyword research trends:  www.google.com/insights/search/