Google recently opened up their AdWords keyword research tool by allowing it to be accessible from outside AdWords accounts. They also added  "global trends" to the Keyword Tool

 Global trends shows the search volume of a particular keyword phrase, charted over a 12 month historical period. To access this data, you can go here and then enter your keyword phrases. Then click the "Get More Keywords", after the page loads, on the right side, select from the "Show columns" drop down menu, the "Global search volume trends" option. You will then see this data charted for you.

Google’s now is feature rich, shows seasonal data, data by match type, and the data is easy to export.