There's an interesting discussion going on in the Haskell mailing list. Despite the source, the focus is on C++ templates (rather than Lisp macros). You'll have to click around; some selected posts to get you started:
One sub-discussion (including posts not yet archived, it lags a day behind) is how to add something similar to Haskell.
There was also a reference to macros in Clean - anyone have more info?
We last discussed macros here
Posted to theory by andrew cooke on 5/24/01; 12:35:13 AM