Many of the SEO people even us, the general people, are sometimes become much eager to know the keyword trend or keyword ranking or sometimes the popularity of keywords or websites. Because if we have to popularize our website, we have to concerned about a few points such as - contents, keywords, ranking etc. As google.com is the most popular search engine today, we generally focus on Google. There are some ways to find popular keywords, most searched terms, increasing searched words etc. Without banging your head here and there, we can use google itself to gather some knowledge.
Have you heard about Google Zeitgeist ? Zeitgeist means "the spirit of the times". Google presents the aggregated results of thousands search queries around the world. There are several tools to look into these data results with the customization, you want.