Headup is a beta firefox addon that provides seamless access to relevant related content as you browse. At the moment Headup requires Silverlight which also refreshingly works on OSX.

Headup uses a range of online content sources (via their respective APIs) “that helps you connect with cool web content related to your interests and friends”.

Once installed Headup simply provides a dotted orange underline below hyperlinks where headup has found related content, hovering over a link displays the headup logo as shown in the twitter screenshot below for @twitchhiker. 

Clicking on the headup logo then opens the headup silverlight window as below that can be used to browse through the related content that headup has found.

The headup blog starts with a post entitled “Semantic Web – an introduction” that provides a succinct overview with a first comment highlighting concerns over privacy. Once installed the headup addon includes a facility to “disable” and all login details to services such as twitter etc. are stored locally.

“Search Engine Land” has a good blog post introducing Headup from October 2008.

Headup can be followed on twitter via @headup and if you are intrigued by @twitchhiker then follow and support him!