How can I make a foam without an immersion blender?
A vita mix should work pretty well; maybe you could carefully drag a spatula in the top of the vortex (nowhere near the blade!) to introduce more air. A whisk will be pretty slow going. And then there is a whole other category of foams made in a whipped cream canister. Here is a link to get you started: http://www.youtube.com/watch?v=c9lJMGImGKE