Searching for keywords is actually easy and free. All you need to do  is open up the Google Adwords Keyword tool to estimate the number of monthly searches, and then test how many pages on the web are optimized for a given word or phrase.  Once you have a term, simply type:

allintitle: (your keyword or keyphrase here)

Into a Google search, and instantly you are presented with the results for all pages on the web that feature that term within the title. This is a fairly accurate way to access the number and quality of your competitors.