Google has released a new Search-based Keyword Tool (beta) that get you a better sense of what your potential customers are searching for and which keywords you should advertise on. The tool is also useful if you don't currently advertise on AdWords. For example, a shoe store could discover which footwear styles users are searching for, or a digital camera blog could decide which cameras to review by looking at which camera models attract the most queries.
The Search-based Keyword Tool is now available to all advertisers in the US and UK. We'll be expanding to additional languages and more countries in the near future.