Since Nicolas mentioned Scala, here is one way to do jitter's solution via JRuby (tested in 1.6 and 1.7):
require 'java'
import 'java.lang.ClassLoader'
f = ClassLoader.java_class.declared_field('loadedLibraryNames')
f.accessible = true
f.value(ClassLoader.system_class_loader).to_array.to_a