In Atlanta some of the buildings and parks are still in use.
The Equestrian facility is quite popular for instance.
The venues that were unable to generate a revenue stream were torn down, such as the white water course.
In Sydney they reconfigured the main stadium and use it for football matches. The sporting facilities remain and are still used. The athletes village became a residential suburb. The olympic precinct remains mostly unchanged from when the games were held. The regatta centre where the rowing was held is still used for rowing as well as a multitude of other sports such as sailing, bike racing and triathlon. The white water course is still there and is open to use by the public.