Google's AdWords Keyword Planner tool is another common starting point for SEO keyword research. It not only suggests keywords and provides estimated search volume, but also predicts the cost of running paid campaigns for these terms. To determine volume for a particular keyword, be sure to set the Match Type to [Exact] and look under Local Monthly Searches. Remember that these represent total searches. Depending on your ranking and click-through rate, the actual number of visitors you achieve for these keywords will usually be much lower.
It arranges your search volume by separating the relevant keywords from those considered irrelevant. It presents those keywords, which it believes would help rank your search engine very high. Once you indicate that you want your keywords to be filtered, the tool would help to arrange that. You know that is very important for your Adsense and adwords campaign. The program is relevant for your CPC and other internet marketing strategies that you want to use.
2) SpyFu: I suggest to have paid account on SpyFu. I just need to find my competitors who using Adwords and review them using this tool. It will show me what ads and keywords they are using. Note that my competitor who paid for that particular keyword knows exactly that it is important for his business including recent trends. Also using SEO feature you can input any URL and find our which keywords they are ranking for.
Recently I had a dilemma with one of my projects, it is related to ecards and many people still using word “cards” instead of “ecards” but Google Keyword Planner and some other tools showed almost the same information for both keywords. At the same time I did not want to have many words “cards” and “ecards” on the landing pages. Semrush helped very much. I found correct data and made a nice PPC campaign.
"I've been doing keyword research for years, and I can tell you that dealing with hundreds of keywords and dozens of spreadsheets is enough to make anyone lose the will to live. Keyword Researcher is great because not only does it let you easily find keywords that people are actually searching for, but it has a clean and simple interface that makes it easy to keep track of what you've found. If I'm stuck and need some new ideas, I just fire it up and usually find several things to write about in a few minutes."
I love Moz’s interface and how they give you data on the keywords. It’s easy-to-read, making it an ideal solution for both experts and newbies alike. They’ll show you both numeric and visual representations of a keyword’s monthly search volume, its opportunity for ranking, priority, and difficulty. They’ll also show you keyword suggestions and SERP analysis, which is fantastic and detailed.

Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website.  In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC).  I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.