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:

Normalise the data entered in several fields. So far firstname, last name... so they are Properly Capitalised What does it do? It modifies profiles and the normal contact edit/add so when you type (or paste) XAV as the first name, it converts it into Xav...
Current Usage: 272
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. ...
Current Usage: 272
Extension to facilitate postcode lookup feature in CiviCRM using AFD, Civipostcode, Experian, PostcodeAnywhere or getaddress.io providers.
Current Usage: 256
Omnipay is an open source payment processor library that supports multiple payment processors (around 30 currently). https://github.com/omnipay/omnipay...
Current Usage: 255
Sagepay using the Omnipay multiprocessor extension.
Current Usage: 255
In version 4.7 and up, CiviCRM ships with only CKEditor, and other wysiwyg editors can be added via extension. This extension makes TinyMCE available as a wysiwyg editor for CiviCRM....
Current Usage: 248
CiviSEPA allows you free SEPA direct debit collections, if you are in Europe.
Current Usage: 243
This extension loads United States counties when you first install it.  Once enabled, it does nothing.  You may disable it or uninstall it, and nothing will happen: the counties will remain loaded in your database.  If you re-enable it, it will check for missing counties and just add those....
Current Usage: 235
This extension adds a pivot report that suppots multiple CiviCRM entities.
Current Usage: 221
Adds over 20 new fields to Summary Fields, including contributions by related contacts, plus fields for CiviMail, CiviEvent, and CiviGrant.
Current Usage: 209
The Advanced Fundraising extension provides a series of reports to help fundraisers view their progress in greater detail....
Current Usage: 206
Creates Tax Receipts with distribution by email or print, detailed reporting, press ready
Current Usage: 205
This extension allows a staff user to add, edit and delete line items of a contribution.
Current Usage: 202
This extension allows to find and export payment(s) for contribution(s).
Current Usage: 183
This extension permits a contact to be changed from one type to another.
Current Usage: 182