How Does A Frogs Skeleton Help It Move?

I was just looking for this myself.  So far, I found that the pelvis can slide (at least in tree frogs) along the lower spine which seems to me like a sort of momentum-building mechanism.  This may allow for a sort of slingshot effect.  In addition, the exceptional length of the leg bones (femur and a fused tibiofibula) combined with it's muscles would give it great power in jumping. An additional interesting fact I found out is that they do not have rib bones; instead, they have a cartilage "plate" that protects their internal organs, presumably from predators and from the impact of landing after each jump.  If you were to view a frog skeleton, the rib-like structures are actually projections from it's vertebra.
Not extremely detailed, but some information none-the-less. :)