Here’s two trend analysis examples from two different sources that I use regularly.
The first is based on job posting keywords which is useful to gauge how marketable your skill set is or how likely you are to find staff given the skills you require. Here’s a simple example. Go Java!
The second is based on search engine requests for given keywords which is useful to gauge interest and popularity of a given framework or api. Here’s a simple example comparing searches for popular Java MVC frameworks.