In Keyword Planner, formerly known as the Keyword Tool, you can get search volume and traffic estimates for keywords you're considering. Unfortunately, when Google transitioned from Keyword Tool to Keyword Planner, they stripped out a lot of the more interesting functionality. But you can make up for it a bit if you take the information you learn from Keyword Planner and use Google Trends to fill in some blanks.
Great Top 10 keyword research tools list. Thank you for posting Robbie! I really appreciated the feedback from the experts. There are a definitely a few tools here worthy of taking note of. I have also been using DYNO Mapper (http://www.dynomapper.com) as a keyword research tool. DYNO Mapper is a visual sitemap generator that delivers keywords on all pages of any site. The user simply inputs any existing URL into the system and it will scan thousands of pages.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input. In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).