gselt watches the X selection and displays a menu of actions that can be done with the text that is currently selected. Actions are configurable and specify regular expressions to match against the selection.
For example, using the sample configuration that ships with gselt, selecting a URI would display this menu:
Selecting a bug number would display this menu:
The menu appears in the top right corner of the screen by default; it can optionally appear under the mouse pointer instead. gselt can also be configured to clear the selection after a button is clicked.