Just came across this really cool lightmapper that also supports loading Irrlicht scenes, I know is not free, but I thought I'd share this here.
It even comes with a 2month trial! http://lightsprint.com/features.html
Yes, you need to send them a mail for the evaluation demo and pricing, I've only used the demo yet and its really great! But the pricing for the full thing is a quite a bit.
I'm still sticking with baking lightmaps in Blender for now. (They still look better than most of dynamic approaches because of the nice Global Illumination one can achieve.)