Whether you’re an online advertiser or content publisher, I think there’s something to be gained from the recently launched Google Trends.
Google Trends
Google Trends graphically displays search volume trends for a keyword (or several keywords simultaneously) for the period dating back up to 2004. Markers on the graphs indicate important events during the period. This is so to let you know what could possibly cause the spike in the graph.
So, could this be useful in the context of internet marketing?
As in the sample figure above, each graph line represents search volume for a particular keyword. Here, the blue keyword consistently commanded a higher search volume than the search volume of a related keyword (denoted by the red graph line). What is more interesting is the fact that the graph also illustrates that there’s a growing search demand for the blue keyword, whilst search trend for the red one seems pretty flat. Also more interesting is you could also now loosely anticipate future search trends based on historical hints.
For the advertiser, the trend comparison information could be useful for planning future ad campaigns.
For the niche content publisher, while this information may not be enough for determining keyword niches, it gives a good headstart of what keywords to do further research on. A keyword with a relatively good volume AND a growing demand seems like a good candidate for futher exploration. What we really need to know is whether the search demands are being adequately met (i.e. via the supply of search results). That’s a whole other exercise but you get the idea. 
Related posts:
Google comes up with fantastic tools!
They’ve upgraded this one with Google Suggest. A much more vast application with advanced features in terms of SEO & PPC relative searches and LSI.