As I previously mentioned, using google's trends you give yourself some ideas, what is mostly talked about on the internet, how often people discuss the subject you chose. It can be really helpful towards money-making titles that can attract more traffic to your website.
How often do you search for say "microsoft" and "linux"? Try the search string: microsoft, linux (separated with a comma). The graph represents the time when the two topics have been mostly talked about. Looks like Microsoft Windows Vista has surpassed the Ubuntu Linux craze, but Ubuntu is steadily increasing - slowly, yet steadily.
This is certainly a utility that's worth to use.