A standardized solution of integrating external applications with Drupal. Service callbacks may be used with multiple interfaces like REST, XMLRPC, JSON, JSON-RPC, SOAP, AMF, etc. This allows a Drupal site to provide web services via multiple interfaces while using the same callback code.
Since our documentation is somewhat lacking on drupal.org, you can watch this for a 1 hour overview of what services is and what it does. http://denver2012.drupal.org/program/sessions/services-inside-and-out
Services 3.0 is now available. Read up on it here.If you want to know more about the new REST server, read here. Note that currently there is no upgrade path for Services 3, and it is not backwards compatible with older implementations of the API. Therefore some existing modules like JSON Server and AMFPHP will not work with it. Fear not, newer AMFPHP modules are in development, and REST Server and JSON Server are no longer needed because response formats have been rolled into Services Core.
- Service API allow modules to create other services, including pluggable access control
- Server API allow modules to create other servers, such as SOAP
- Aliasing methods
- Integration with core Drupal functionality like files, nodes, taxonomy, users, files and more.
- Response format API allows you to define response Formats for CONTENT-TYPE ie. application/json or application/xml. (also calls such as ENDPOINT/node/1.json work)
Note services for drupal 6 is no longer supported because of https://drupal.org/node/2012982 and https://drupal.org/node/2125265. If anyone wants to become a maintainer for service d6 please contact a member of the services team in #drupal-services and provide a working backport of the patch applied to drupal 7 services.
Currently spyc has an upstream bug please the version of the code on this issue until the upstream patch has been committed if you reference any error messages
Feel free to edit/fork/comment on this list of examples https://gist.github.com/affc9864487bb1b9c918
For modules with services support goto https://drupal.org/node/750036. Note anyone can add to this list.