http://drupal.org/project/restws

Exposes Drupal resources (e.g. entities) as RESTful web services. The module
makes use of the Entity API and the information about entity properties
(provided via hook_entity_property_info()) to provide resource representations.
It aims to be fully compliant to the REST principles.

* To obtain the JSON representation of an entity use your browser to visit

http://example.com/node/1.json or
http://example.com/user/1.json or
http://example.com/[entity type name]/[entity id].json