TXL is the best I've seen for transforming ASTs (sample: http://www.txl.ca/tour/tour9.html). As you can see, it's a little complex, which is because the problem is complex. I think they do a really good job. (TXL homepage http://www.txl.ca/)

Also: I recall Matz said Ruby was lisp with friendlier syntax (but I can't find the quote right now, so maybe he didn't).