Super Secret Spy Keyword Research
Despite subscribing to numerous keyword services and "spy" services myself, I've found that one of the best tools to finding the motherload of actual keyword phrases, including longtail terms no one else thinks to bid on or build a page around ---- is free.
It's your own stats from your ISP. For many, its as simple as logging into your cpanel, clicking to your awstats log, and then reviewing the keyword phrases recorded by your ISP.
You can view how many times a keyword has been used, and segment your search by month or for the entire year.
Best of all, only you have this data.
And its often much better information than what you can get from a paid "spy" service. For example, I have a specialized legal niche involving non-compete agreements. You know what information I get from third party services involving noncompete related terms? Either squat or a couple generic terms. But my own webhosting stats give me hundreds of phrases that I can bid on or use to create feeder pages.
As for the "spy" services telling you every keyword someone else is bidding on, have you ever run one on yourself? From my experience, they're utter crap. Either I'm not bidding on the keywords they say I'm bidding on, or they don't come close to getting my list.