Order here. Ticket prices range from $44 to more than $3000, but never fear, supposedly there are some free viewing areas for the marathons and the cyling part of the triathlon.
Tickets are on sale until April 26 and are not processed until that time, so are not first-come, first-served. Events that are over-subscribed will be handled by random ballot. And if you go, don't forget to take your Visa card!