Ok, well I'm going to give this a go. As always though it's a matter of having enough time to work on it!!
I'll be using Maya Unlimited 6, possibly Photoshop and maybe even Syntheyes + Digital Fusion for a mix-with-live-action version if there's time for that!
My initial thoughts are to do the main bulk of the avalanche using Fluid Effects, the missile-like bits that shoot out forwards occasionally with particles, the rocks and other debris including the building as rigid bodies and then maybe some trees as a dynamics/Paint Effects combo. Rendering will most likely be done in Mental Ray.