Forum OpenACS Q&A: Continuations, coroutines, threads, etc.
Coroutines and continuations are related concepts. Roberto Ierusalimschy's papers include his 1994 "Revisiting Coroutines", with a very nice overview of coroutine stuff. It seems to touch on every flavor of coroutine other than Simon Peyton Jones's "cheap continuations". (He's also the creator of Lua.)