Keywords, Keywords, Keywords: Some for Free, Some for a Fee

Good Keywords is a free Windows software program for finding good keywords for your web pages.
Targeting the right keywords equates to targeting the right audience; you need to have the keywords on your page that your market is searching for in order to be found and indexed by the search engine spiders.
Good Keywords is completely free. No registration, no payments, not even an e-mail address to enter. It is a small 500Kb download, digitally signed and safe to install. Good Keywords was originally published in August 2000 as freeware and has remained free ever since. Get it by clicking the link below:

http://www.goodkeywords.com/

Wordtracker
If you need more extensive keyword research, you should consider using what professional SEOs use: Wordtracker.
Wordtracker helps website owners and search engine marketers identify keywords and phrases that are relevant to their or their client's business and most likely to be used as queries by search engine visitors.
Marketers can also determine how many competing sites are using those keywords and can identify the phrases that have the greatest traffic potential.
You can get a free trial, or sign up for a year, a month, a week, or a day at a time.
Check out Wordtracker at: Wordtracker.com.

Wordtracker Magic
For an excellent resource on getting the most out of Wordtracker, check out Wordtracker Magic - Discover the Best Keywords in a Matter of Seconds by John Alexander of Search Engine Workshops.