I have already diligently searched google, and now I'm looking for
recommendations.

Does anyone know of an app for capturing text from screen?  (I'm using
Gnome on RH9).  Example:  Mozilla provides a very useful display of
links under View-->Page Info-->Links.  But there is no way provided by
Mozilla to copy and paste, or just "grab" that information (AFAICT).  I
can sort of "select" the rows, but can't seem to copy and paste it.

I want that list of links.

Now: I can do a screenshot with the Gimp, then OCR that image... but
that seems like a very multi-step way of doing it.

Screen-capture programs are all over the Windows world.  Snag-it is a
good example.  Heck -- even Sidekick 1.0 let you select a portion of a
DOS screen and output it as text.  Anything like this in the Linux
world?  If it's text on my screen, I want to grab it.