Now here’s a recipe that doesn’t sound half bad: Peanut Butter Porter v0.1, from the SleezySherm Breweries weblog. He took steps to minimize the amount of oil going into the beer; I don’t think you can completely remove the oil from peanut butter, and it’s the oil that prevents head forming/retention. I’ve read homebrewing advice that advocated just staying away from peanut butter to avoid this type of hassle.

Of course, you could always try skipping the peanut butter and processing peanuts directly, or other nuts (hazelnuts are relatively common in beer). One method of doing this (at least with hazelnuts, if I remember correctly) is grinding them up and steeping them in vodka to extract the nut "essence," and adding that to the brew as a flavoring agent (during fermentation, not at the boil). I’ve never tried it myself.