Linux Screen Scraper

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.