From Greg Benage:
"A typical 1-lb. charge of plastic explosives has a blast radius of 15 ft., deals 5d6 points of damage, and costs 100cr. Reflex save for half for anyone caught in the blast radius. Each additional pound of explosives added to the charge increases the damage by 2d6 and increases the blast radius by 5 ft.
If you set a shaped charge (+5 DC on the Demolitions check), the blast radius is reduced to 5 ft. and the damage is doubled. For each additional pound added to the shaped charge, you get +2d6 damage and +5 ft. on the blast radius. In this case, treat the area of effect as a cone originating at the point where the charge is placed."
He also said there will be lots of explosive charges in the Imperial Supply book.
Mike