First off, you can email Marty here. He likes getting email.
You can also find Marty on Flickr, MySpace, Facebook, and a few other places. (No sense in giving away all the mystery.) He’s also using Twitter now (God help you all). He does regular work with Ideaschema (living, as he does, with the Ideaschema Lady Her-Own-Self), and can be contacted through those channels as well.