I've roasted them, either in the oven or on the grill (whole, peel on) and then peeled and frozen the pulp. I use it either for baigan bhartha or baba ganoush (drain it after it defrosts) and it seems to work well. Never tried it purged/still raw as Alton suggests. I may have to give it a try as it would sure be nice to have it frozen when I want slices versus pulp.
I will say skip the plastic wrap that is suggested as they grow mold rapidly when wrapped like that. I've actually quit buying them at one store here because they're almost always packaged like that, and either moldy at the store or grow it within a day. I suppose you could guess that just means they're old but they'll do it even when they're still quite nice looking and firm otherwise so I've always blamed it on the plastic wrap.
For those in touch with it, Reality is the leading cause of stress.