Extensions are installable packages which give CiviCRM new functionality, and this directory provides a centralized list of extensions which the CiviCRM community has created.

Further resources:

This module makes it easier to configure settings in CiviCRM by:...
Current Usage: 32
This module makes it easier to configure settings in CiviCRM by  ...
Current Usage: 32
Integrate Direct Debit payments using SmartDebit (https://www.smartdebit.co.uk/) with CiviCRM
Current Usage: 31
This CiviCRM extension provides two way synchronisation between CiviCRM groups and MailChimp Lists. Changes to users in regular groups are synced with MailChimp in real-time, smart groups use CiviCRM's Scheduled Jobs to sync up. Changes made on MailChimp are sync'd back to CiviCRM using Webhooks...
Current Usage: 29
SYSTOPIA OpenStreetMap CiviCRM Geocoder This CiviCRM extension adds the Nominatim OpenStreetMap server as a geocoding option. Just install the extension, and activate via "Administer" => "System Settings" => "Mapping and Geocoding"....
Current Usage: 28
This CiviCRM extension allows you to limit the display of individual prices in price sets to specific groups. This allows you to implement things like members-only pricing for events. (by using a Smart Group to track current members) This extension works with both static and smart groups....
Current Usage: 27
CiviRelate creates a CiviCRM relationship between the acting user and a CiviCRM contact created by the acting user through the submission of a designated CiviCRM profile form. CiviRelate has a simple configuration page to define the Profile to use and the relationship to create....
Current Usage: 26
CiviCRM extension for Dutch postcode checking
Current Usage: 26
  Contact Calendar is a CiviCRM extension that displays activities where the contact is an assignee or a target contact. The calendar is useful when the activities are in the future and people can plan thier schedule.  ...
Current Usage: 23
This module allows for taxonomy vocabularies and terms in Drupal to be mirrored with groups in CiviCRM....
Current Usage: 22
This module allows for content types in Drupal to be mirrored with groups in CiviCRM. Dependencies This module requires the CiviCRM module....
Current Usage: 21
PDF API for CiviCRM to create a PDF file and send it to a specified e-mail address. This is usefull for automatic generation of letters The entity for the PDF API is Pdf and the action is Create. Parameters for the api are specified below:...
Current Usage: 21
Adds the ability to setup recurring payments for contacts through the administration interface....
Current Usage: 20
Small helper module for migrating a CiviCRM database for v 4.2 or lower....
Current Usage: 20
Sunlight Congressional Districts - Fetches data about the current members of Congress using the Sunlight Congress API.http://services.sunlightlabs.com/docs/Sunlight_Congress_API/...
Current Usage: 20