IIRC, GnuCash and LilyPond use Guile. The project itself now has some good maintainers, and has been making strides since its 2.0 release. Some parts of the (small) Scheme community have taken notice, and new projects are popping up; like GNU Artanis[0].
For a long time -- until Andy Wingo took over development -- Guile was kind of a joke of a Scheme. It was horrendously slow and buggy, and it was updated very infrequently. Since Andy took over, it's quickly become one of the better choices for Scheme. Guile 2.0 is solid and reasonably fast. The 2.2 release is shaping up to be even better and even faster. Andy has done a great job with it, and he keeps his blog[0] updated with a lot of interesting posts about Guile internals and development.
Oh ah, and there's Guix[1].
0: http://web-artanis.com/
1: https://www.gnu.org/software/guix/