My first laughable attempt at a page breaker for balancing columns. Doesn't work if the element list fits into the first available area and doesn't balance exactly like I would like it to when the balancing actually gets active. But it's better than nothing to start with.
xmlgraphics/fop/trunk/src/java/org/apache/fop/layoutmgr/BalancingColumnBreakingAlgorithm.java