Awesome

Apart from the classics like Lilypond and Gnucash, which use Guile as an extension (and are now suffering from growing pains due to the radical changes in their extension language -- but there is the will to resolve that), here's something "new" and "shiny" for you:

AO: algorithmic 3D CSG: <http://www.mattkeeter.com/projects/ao/>
Lepton-EDA <https://github.com/lepton-eda/>

Plus, of course, web servers and things. I particularly like Tekuti, Andy Wingo's "blogging engine".

And, of course, Guix (which is "just" a functional clone of Nix. The basic ideas and some code is stolen from there: kind of the Git of package managers).

This new push in Guile is since a while in the works: last year's FOSDEM was already notable, but this year even more.