Drupal 7.x-dev / 6.13 / 5.19

Major Features :

1. Collaborative Book Our unique collaborative book feature lets you setup a "book" and then authorize other individuals to contribute content.
2. Friendly URLs Drupal uses Apaches mod_rewrite to enable customizable URLs that are both user and search engine friendly.
3. Modules The Drupal community has contributed many modules which provide functionality that extend Drupal core.
4. Online help Like many Open Source projects, this has built a robust online help system built into the core help text. Available to you on your own site.
5. Open source The source code of Drupal is freely available under the terms of the GNU General Public License 2 (GPL). Unlike proprietary blogging or content management systems, Drupals feature set is fully available to extend or customize as needed.
6. Personalization A robust personalization environment is at the core of Drupal. Both the content and the presentation can be individualized based on user-defined preferences.
7. Role based permission system Drupal administrators dont have to tediously setup permissions for each user. Instead, they assign permissions to roles and then group like users into a role group.
8. Searching All content in Drupal is fully indexed and searchable at all times if you take advantage of the built in search module.
9. User authentication Users can register and authenticate locally or using an external authentication source like Jabber, Blogger, LiveJournal or another Drupal website. For use on an intranet, Drupal can integrate with an LDAP server.
10. Polls Drupal comes with a poll module which enables admins and/or users to create polls and show them on various pages.
11. Templating Drupals theme system separates content from presentation allowing you to control the look and feel of your Drupal site. Templates are created from standard HTML and PHP coding meaning that you dont have to learn a proprietary templating language.
12. Threaded comments Drupal provides a powerful threaded comment model for enabling discussion on published content. Comments are hierarchical as in a newsgroup or forum.
13. Version control Drupals version control system tracks the details of content updates including who changed it, what was changed, the date and time of changes made to your content and more. Version control features provide an option to keep a comment log and enables you to roll-back content to an earlier version.
14. Blogger API support The Blogger API allows your Drupal site to be updated by many different tools. This includes non-web browser based tools that provide a richer editing environment.
15. Content syndication Drupal exports your sites content in RDF/RSS format for others to gather. This lets anyone with a News Aggregator browse your Drupal sites feeds.
16. News aggregator Drupal has a powerful built-in News Aggregator for reading and blogging news from other sites. The News Aggregator caches articles to your MySQL database and its caching time is user configurable.
17. Permalinks All content created in Drupal has a permanent link or "perma link" associated with it so people can link to it freely without fear of broken links.
18. Apache or IIS, Unix / Linux / BSD / Solaris / Windows / Mac OS X support Drupal was designed from the start to be multi-platform. Not only can you use it with either Apache or Microsoft IIS it also has Drupal running on Linux, BSD, Solaris, Windows, and Mac OS X platforms.
19. Database independence: Drupal is built on top of a database abstraction layer that enables you to use Drupal with MySQL and PostgreSQL. Other SQL databases can be supported by writing a supporting database backend containing fourteen functions and creating a matching SQL database scheme.
20. Multi-language Drupal is designed to meet the requirements of an international audience and provides a full framework to create a multi-lingual website, blog, content management system or community application. All text can be translated using a graphical user interface, by importing existing translations, or by integrating with other translation tools such as the GNU gettext.
21. Analysis, Tracking and Statistics Drupal can print browser-based reports with information about referrals, content popularity and how visitors navigate your site.
22. Logging and Reporting All important activities and system events are captured in an event log to be reviewed by an administrator at a later time.
23. Web based administration Drupal can be administered entirely using a web browser, making it possible to access it from around the world and requires no additional software to be installed on your computer.
24. Discussion forums Full discussion forum features are built into Drupal to create lively, dynamic community sites.
25. Caching The caching mechanism eliminates database queries increasing performance and reducing the servers load. Not only can the caching be tuned in real time, while your site is under load, but it has been successfully tested under a "slashdotting" and performed extremely well.

Enhancements:

1. 6.13 Changes:
   • Fixed documentation glitch.
   • JavaScript string split() function does not behave like PHP explode(); causes problems with multiple node body break tags
   • _drupal_flush_css_js() should not have q as a possible CSS query character, since that is the Drupal path name character too
   • Names of compressed CSS and JS files should have a prefix, so that names starting in ad* will not happen. Those are easily blocked by firewalls, Firefoxs Adblock, etc.
   • cache_clear_all() mentioned cache_flush_delay incorrectly; it  uses cache_lifetime
   • drupal_set_title() in forum_overview() is not needed; menu already sets the title and is localized
   • Password equality checking was not using strict type checking; it assumes these are strings and compared character to character
   • Fixed grammar in forum module messages
   • Fixed module support for disabled module update status checking and do not track usage in that case.
   • The Anonymous name is a plain text setting, so it should be escaped properly for output.
   • Actions set to run on cron were not actually triggered.
   • Show the node access rebuild button. The check on when to show it was fragile, so the button might not have been there when actually needed.
   • For proper HTTP query simple testing, it passes on the instance identifier (database prefix).
   • Save a query by only calling file_space_used() when a limit is provided.
   • The serialize Schema API property was used but not documented.
   • The session.use_cookies PHP setting is required by Drupal, but it can be turned off, so try to ensure it is turned on at all times.
   • When changing columns, PostgreSQL needs explicit type casting to ensure that values are kept properly.
   • In system_clear_cache_submit(), the function arguments were swapped (but it did not affect how it actually worked).
   • Update status should not attempt to request update data until a limit is reached. Fixed Drupal instances when drupal.org is down and gets less load on Drupal.org if data is not found.
   • Remove url() wrapping from remote links and link in a more user friendly OpenID provider list.
   • Use filter_xss_admin() on site name and site slogan, just like footer message and mission
   • Fix drupal_mail() documentation, so that it encourages to set the body of the email as an array (like core does).
   • The tablesort code did not account for possibly nested tables; only match immediate descendants, so elements of nested tables are not matched.
   • The safe string check on translations should only be applied to the default textgroup. Strings in other textgroups such as blocks and menu items are displayed via escaping and filtering, and might contain arbitrary HTML.
2. 5.19 Changes:
   • hr should be treated as a block level tag. Backport by alexanderpas.
   • The session.use_cookies PHP setting is required by Drupal, but it can be turned off, so try to ensure it is turned on at all times.