sjmiller said:
If a character is picked up by an elemental, what can the character do during its turn? How many characters can a Huge elemental carry at once? Can it move through a party and scoop up everyone in a single turn?
Anyone caught by a whirlwind is generally free to act on their turn, but cannot move except to try to escape (which they can only do if able to fly). They suffer a –4 penalty to Dexterity, and a –2 penalty on all attack rolls; if they attempt to cast a spell, they have to make a Concentration check (DC 15 + spell level).
To escape, a flyer has to make a Reflex save (the DC is the same as it was to avoid getting picked up); if it makes the save, it still takes damage but can leave the whirlwind on its turn. Creatures who cannot fly are generally at the elemental's mercy, unless they have the means to destroy it, nullify the whirlwind, or gain some sort of control over the elemental.
As for how many people it can hold? Well, that's a little more complicated. A Huge air elemental in whirlwind form can hold as many as 105 Medium creatures in it, if you figure a Medium creature as taking a 5-foot cube. The first ten feet (at the base) only carries one such creature per cube; at elevations 15' and 20', it holds five each (forming a cross). At 25' and 30', it holds 9 each (forming a 3×3 square); at 35', it holds 13 (forming a diamond shape). 40', 45', and 50' each hold 21 (a 5×5 square with the corners cut off).
I made a SketchUp file that shows all this; I can make screenshots to post here, or send you the file directly (you can see it best using the Section Plane and dragging it up and down).
As for scooping up a party, sure thing. It doesn't provoke attacks of opportunity, and anyone who fails that second Reflex save gets pulled up. Once they're within the whirlwind, the elemental can put them pretty much wherever it wants inside it, and can keep hold of them as long as it likes (unless they can fly on their own).