Darcy,
For whatever reason, Google really doesn't want to give us the keyword search data that they have. However, Microsoft is actually taking a different approach, where they give us the ACTUAL search numbers, and even will predict it in the future. If you have access to MSN AdCenter, you can get that data. I prefer to use the Bing Advertising Intelligence to pull the data into MS Excel and then crunch the numbers from there. You can start with a keyword list from Google AdWords, put the data into MS Excel, and then get the real numbers of queries right there in Excel. Then, you can calculate possible Google search queries by multiplying by their current market share percentage.