It doesn't matter what kind of marketing you are involved in.
Having most keywords for your market or niche is a surefire way to win over your competition, and that's a fact!
The most important place to have thousands of keywords is in your pay-per-click campaigns, as you want to hit as broad an audience as possible, within your market or niche.
If you are using pagemill software to automatically build websites surrounding a particular market or niche, you know that more keywords you have, more pages your site will contain, and ultimately higher pagerank and position your site will have.
Therefore, having as many keywords as possible is absolutely critical to your online success.
Luckily, there are a several free resources you can use in your quest.
3 Great And Free Keyword Resources
The most widely known resource is Overture's Keyword Tool:
Type in a phrase and all related searches on yahoo for past month will be yours for taking.
Another great resource is Google's Keyword Tool:
Simply type in your phrase and out comes a large list of related searches on Google.
What's even more cool is that Google's Keyword Tool will also give you a list of similar searches. These may not be exactly for your market, but they will be highly revelant none less.
The Last Free Keyword Tool is Good Keywords:
This is actually a free piece of software that you download and install of your computer.