Probably not the module you're looking for, but then again you're not going to be able to turn any of the others in for your homework either . . .

module Main
    where

eng_commafy :: (Show a) => [a] -> String
eng_commafy x | length x > 2  = foldl1 (commacat) init_as_show ++ ", a
+nd " ++ last_show
                                where
                                  commacat x y = x ++ ", " ++ y
                                  init_as_show = map (show) (init x)
                                  last_show    = show (last x)
eng_commafy x | length x == 2 = (show (head x)) ++ " and " ++ (show (l
+ast x))
eng_commafy x | length x == 1 = show (head x)
eng_commafy [] = ""


main = do
    putStrLn (eng_commafy [1..10])
    putStrLn (eng_commafy [1,2])
    putStrLn (eng_commafy [1])
[download]

(Yeah, my Haskell's terrible . . . :)

Update: Actually looking at the OP's posting history this is probably not homework. But it's still trivial and probably not past the threshold of "should be stuck in a module" on its own.