There has been a revolution of keyword research tools over time. The first introduction to keyword research for most of us was years ago with the free overture keyword tool, which was the basis for many an early PPC campaign. Overture became Yahoo and provided insight into Yahoo’s keyword “inventory.” it was revolutionary.
Now with more advanced tools like Trellian Keyword Discovery, and WordTracker we have access to databases of differing sizes, quality, focus, skew and insight. aimClear suscribes to several regionl, global, and specialized keyword databases (through their APIs) which we aggregate in a proprietary tool. However WordTracker offers a free keyword research tool with useful functionality to the public. If you’re willing to do a little screen scraping, data can be harvested to provide insight into the keyword universe.
Keep in mind that you are not looking at annual search frequency in the results. The numbers returned in WordTracker’s free keyword research tool reflect he search total in WordTracker’s database over the previous 90 days which is a relatively small sampling of actual Internet searches. However the statistics are a very useful weighted rendering of keyword importance. WordTracker is one weapon in most SEM firms’ arsenal of keyword research tools.