One of the first successful PPC ad systems was service called Overture. One of the most popular features of this service was a tool called the Search Suggestion Tool. Anyone online back in say 2002-2003 used this tool a bunch to help determine what search phrases received the most traffic. This was one very simple DIY tool.
When Yahoo bought out Overture the tool languished and eventually went away. In my opinion this was a big mistake on the part of Yahoo. (But that’s a conversation for another day)
Click on the screenshot below to see full size
Google recently enhanced their keyword suggestion tool and added search volume and some measure of competitiveness. The reason the PPC engines offer tools like this is to help people get better at bidding on search terms and offer suggestions for more terms to bid on. Serious PPC folks use this tool to help determine bid amounts and bid on thousands of search terms. (If you have an AdWords account this tool is built into your dashboard.)
I’ve found that this tool is also a nice, low effort way to get some ideas for keyword phrases for your web pages and blog posts. The tool offers suggestions for ways that people are really searching in your industry and might spark some ideas for blog headlines. Of course, for local businesses, this can be a great way to identify terms that you might want to add your city name to.