Much of the present-day popularity of alliterative verse is connected to the work of Christian authors, in particular, members of the Inklings group at Oxford. Most of this impact came through the work of J.R.R. Tolkien and C.S. Lewis (though another Inkling, Neville Coghill, who served as W.H. Auden's tutor, is known for his translation of Piers Plowman. Both Tolkien and Lewis had a significant public impact. Tolkien's had a greater impact on the general public, through the publication of Lord of the Rings, and posthumously, through Christopher Tolkien's edited editions of The Silmarillion, The Lays of Beleriand, and The Fall of Arthur. C.S. Lewis had more of an impact on the Christian community through works like Mere Christianity and The Screwtape Letters, and (for the most interested), his posthumous collections, Poems and Narrative Poems. Since both Tolkien and Lewis loved alliterative verse, their willingness to read and write in alliterative verse has also been transmitted in Christian circles.
Note: The poetry linked here may range in quality from novice work to brilliant. It is probably just the tenth of the iceberg that shows above the ocean. There is almost certainly much more out there. Send me links if you find them ... use the following email, making the standard substiution: pdeane[at]alliteration.net