One of my favorites was from church. When I was a child and the congregation sang The Doxology ("Praise God, From Whom All Blessings Flow") I always heard "Praise him all preachers here below." Makes sense, right? The real words, of course, are "Praise him all creatures here below."
Other new entries in Merriam-Webster's dictionary are "webinar" (an live online educational presentation) and "pescatarian" (a vegetatarian whose diet includes fish).
Post your favorite mondegreen in the comments.