This influence/importance can also be seen in the existence of GeoDjango, which is shipped with Django itself[0], where Ruby seems to have the old GeoRuby[1], the rather recent (and with unsure following) RGeo[2] or doing raw PostGIS.
Also in OpenGEO, looking at their projects, aside from PostGIS it's either Python (and JS) or Java (and JS)
[0] https://docs.djangoproject.com/en/dev/ref/contrib/gis/
[1] http://rubyforge.org/projects/georuby/
[2] http://dazuma.github.com/rgeo/