Internationalization support. A message catalog to store translated text, localization of dates, number formatting, timezone conversion, etc. Allows you to serve your users in their language.

External authenticaiton. Integrate with outside user databases through e.g. LDAP, RADIUS, Kerberos, MS Active Directory. Imports user information through IMS Enterprise 1.1 format. Easily extended to support other authentication, password management, account creation, and account import mechanisms. This includes improvements to the basic cookie handling, so logins can be expired without the user's identity being completely lost. You can set login to expire after a certain period (e.g. 8 hours, then password must be refreshed), or you can have all issues login cookies expired at once, e.g. if you have left a permanent login cookie on a public machine somewhere.

User interface enhancements. All pages, including site-wide and subsite admin pages, will be templated, so they can be styled using master template and site-wide stylesheets. We have a new default-master template, which includes links to administration, your workspace, and login/logout, and is rendered using CSS. And there's a new community template (/packages/acs-subsite/www/group-master), which provides useful navigation to the applications and administrative UI in a subsite. In addition, there's new, simpler UI for managing members of a subsite, instantiating and mounting applications, setting permissions, parameters, etc. Site-wide admin as also seen the addition of a new simpler software install UI to replace the APM for non-developer users, and improved access to parameters, internationalization, automated testing, service contracts, etc. The list builder has been added for easily generating templated tables and lists, with features such as filtering, sorting, actions on multiple rows with checkboxes, etc. Most of all, it's fast to use, and results in consistently-looking, consistently-behaving, templated tables.

Automated testing. The automated testing framework has been improved significantly, and there are automated tests for a number of packages.

Security enhancements. HTML quoting now happens in the templating system, greatly minimizing the chance that users can sneak malicious HTML into the pages of other users.

Oracle 9i support.

Who's online feature.

Spell checking.

With the release of OpenACS 5, PostgreSQL 7.2 is no longer supported. Upgrades are supported from OpenACS 4.6.3 under Oracle or PostgreSQL 7.3.

The undocumented special handling of ~ and +variable+ in formtemplates, found in packages/acs-templating/resources/*, has been removed in favor of using <noparse> and \@variable\@ (the standard templating mechanisms). Locally provided formtemplate styles still using these mechanisms will break.

Serving backup files and files from the CVS directories is turned off by default via the acs-kernel parameter ExcludedFiles in section request-processor (The variable provides a string match glob list of files and is defaulted to "*/CVS/* *~")