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:

http://drupal.org/sandbox/leez/1929728 A drupal module for querying a CiviCRM database for donor patterns (overview, new, lapsed, upgraded, downgraded, maintained) and producing CSV files from the results....
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This extension sends sms as a autoreply when Inbound SMS activity is recorded.
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This CiviCRM extension provides a daily scheduled job named "Call Email2Each.Sendemails API (Daily)"  This job expects 2 parameters: a group name and a message template name.  When this job runs,  it will send an email to each contact in the group/smart group. The contents of the email will be the message template. ...
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The recurring contribution search adds a custom search to CiviCRM in which a user can search for recurring contributions.
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processor plugin but no longer recommended
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Clone existing event registration
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When viewing reports, clicking on a contact's name brings you to the contact's record, not their Contact Detail Report or Contribution Detail Report....
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This extension adds functionality to add attachments to message templates. You can add attachments to templates by editing the message templates under Administer --> Communication --> Message templates. Updating a template through the e-mail screen does not work....
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This is an integration module for sites running CiviCRM and the Domain Access module.  By default, when creating a user in Drupal, Domain Access will automatically assign the user to the domain on which they registered.  However, if they create their user via a CiviCRM profile, they will not be added to the appropriate domain.  This module fixes that....
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CiviCRM native extension to check if the CMS is in maintenance mode when I get a REST API and return error if so.
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This extension helps you creating custom API's that retrieve query result data. If an external application needs information from CiviCRM that cannot be expressed using API parameters, you can use this extension. It allows you to create a custom API that returns data from an SQL query, in a way that you can use API filters, options and joining as always....
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CiviCRM-Secure-Trading-Payment-Processor for CiviCRM 4.3...
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This very tiny extension enables validating a checksum (combination of contact_id and checksum) with an API.
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When a home address for an Individual contact in Austin, Texas is added to CiviCRM when importing or manually this extension finds its City Council District using shape files produced by the City of Austin Texas and GEOS - Geometry Engine, Open Source and sa...
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PayZang has developed a payment processor plugin for CiviCRM (4.2.9) on Drupal that allows organizations to accept ACH and Credit/Debit Card payments. This plugin allows you to do recurring as well one-time payments using both ACH and Credit/Debit Cards....
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