ActoTracker is an application for keeping track of activities on your desktop so that you don't have to. Think of it as an app for bookmarking desktop documents and applications. It can also bookmark things that are not usually tied to a URL such as Outlook email message or Filemaker records. It can be extended to handle additional applications by writing custom AppleScript plugins. ActoTracker is somewhat inspired by the GNOME Activity Journal (Zeitgeist framework), and it tries to solve a similar kind of problem for the end user, although in a different way.
The LinCastor enables you to register your own custom URL scheme (e.g. mylink://foo/bar) and associate it with an application, shell, or AppleScript handler. As most OS X application support embedding links as part of a text, custom URL schemes provide a great way to connect different applications together or trigger custom workflows. For example: a link jira://issue1234 could open a JIRA tracker with specific issue. Another use is to associate well knows URL schemes with specific application. For example: firefox-http://www.mysite.net would open http://www.mysite.net in the Firefox instead of the default browser.
Tactor is a tool that tries to guess the best action for the current text selection. For example, text containing http://xyz.com is recognized as an URL link, and ~/Documents/MyPresentation.key as a presentation file. Both matchers and actions are fully customizable. It is loosely based on Plan9ís Plumber where any text can potentially be an action, although the actual technical implementation is very different. It provides functionality somewhat similar to that of Apple Data Detectors in a way that is fully extensible and transparent.