[koalahedron]

Furthermore, to get an Emacs-like REPL (Edwin)

  1 ]=> (edit)

  ;Loading "/usr/lib/x86_64-linux-gnu/mit- 
  scheme/lib/prx11.so"... done

[vitus]

I usually just open up a *scratch* buffer in emacs, and use ctrl-J to evaluate expressions.

I think my most common use case is for math (e.g. adding values that I extracted via some emacs keyboard macros).