gistfile1.txt

in an EntityListener:

    @Override
    public void onEntityCombust(final EntityCombustEvent event) {
        if (event.isCancelled() || !(event.getEntity() instanceof Player)) return;
        DamageReport.recordCombuster(event);
    }

in DamageReport:
    static void recordCombuster(final EntityCombustEvent event) {
        if (event instanceof EntityCombustByEntityEvent) {
            EntityCombustByEntityEvent byEntity = (EntityCombustByEntityEvent) event;
            DamageReport.combuster.put(event.getEntity(), DamageReport.describeEntity(byEntity.getCombuster()));
            return;
        }
        
        System.out.println(event instanceof EntityCombustByBlockEvent);
        if (event instanceof EntityCombustByBlockEvent) {
            EntityCombustByBlockEvent byBlock = (EntityCombustByBlockEvent) event;
            DamageReport.combuster.put(event.getEntity(), DamageReport.describeMaterial(byBlock.getCombuster().getState().getData()));
            return;
        }
    }

when a Player walks into lava and back out again, in console:
2012-01-08 17:41:15 [INFO] false