Over at Lambda the Utimate they're featuring the classic paper Representing Control in the Presence of First-Class Continuations by Dybvig and Bruggeman. I remember reading this paper years ago at a time when I was still wrestling with the notion of continuations and how they worked. While reading the paper, everything suddenly snapped into place and it all made sense. If you're a Scheme programmer and you haven't read this paper yet, you should. You'll be glad you did.