When you write a blog entry, you often take time to search image, referenced links, definitions from wikipedia, related articles .... to insert into the entry content. You do that because you know that rich content will make your reader more excited and inspire them to visit your blog more often. Zemanta is a tool to help you do that easily.
I know this tool when I developed a web 2.0 site for blogger community 1 year ago.
Have a look on an entry content decorated with Zemanta:
Zemanta currently get the decorated content from 20 different sources: Wikipedia, Flickr, Youtube, ... and supports integration with most blogging platforms.
To use this tool, you can choose below options:
1. Install a plugin for browser (currently it supports plugin for Internet Explorer and Firefox)
2. If you use Windows Live Writer, it also has a plugin for you.
3. If you develop a blogging service or host your own blog with Wordpress, Drupal, it has some server side plugins for you.
How to use this tool: just try a demo here