Robin Parry has some information about that on his blog, but I don’t remember where. Shouldn’t be hard to find, and it involves a video interview with Plantinga, so there should be relevant quotes to mine.
Also, our friendly competition over at the Evangelical Conditionalism blog is a good source for finding annihilationists.
I guess as the resident Lewis expert I should write a brief blurb for him.
Lewis, Clive Staples (1898-1963), British philosopher and professor of English literature, converted from atheism to become arguably the most influential Christian apologist of the 20th century. Taught that even those who formally oppose Christ in this life may in fact be secret Christians and would enter heaven (such as the character of Emeth in The Last Battle). Strongly speculated (such as in The Great Divorce) that God would save some (but not all) previously impenitent sinners post-mortem after some mode of purgatorial punishment. Proposed a unique theory (in The Problem of Pain) merging eternal conscious suffering with annihilation: the sinner may continue to exist in relation to God’s eternal existence but ceases to exist from the timeline reality of God’s creation. Otherwise usually trended more toward annihilationism than eternal conscious suffering. Final theological statement in his final work of theology (Letters to Malcolm: Chiefly On Prayer), in regard to his affirmation of purgatory: “If this isn’t true, something better will be.”
I’m pretty sure his stepson evangelist Douglas Gresham, on the other hand, is at least a hopeful Christian universalist–I heard him lecture in person once (at a Baptist university) shortly before my own switch and was amazed to hear him basically affirming someone’s universalistic interpretation of Romans 5. Will try to find some more information on him.