Web interfaces to SpamAssassin
Generic
webuserprefs [http://sourceforge.net/projects/webuserprefs/] This PHP front-end support web-based administration of both file-based and SQL installations, and a number of authentication options. Detailed configuration directions are [wiki:Self:SingleUserUnixInstall#head-1dd15c06b7e645638def3d2ed2ef31557d853659 available].
[http://www.maiamailguard.com Maia Mailguard] is a web-based interface and management system for the popular amavisd-new e-mail scanner and SpamAssassin. Written in Perl and PHP, Maia Mailguard gives end-users control over how their mail is processed by virus scanners and spam filters, while giving mail administrators the power to configure site-wide defaults and limits.
[http://www.vmailadmin.org vMail.Admin] is a web-based interface and management system for Postfix and SpamAssassin servers using SQL for storage. Written in PHP and Perl, vMail.Admin gives administrators control over global, per-domain and/or per-user settings while providing the same control to end users to manage their own SpamAssassin settings. Administrators are not limited to the default SpamAssassin option available through vMail.Admin since vMail.Admin gives administrators the ability to add and/or removed any valid SpamAssassin option.
For SQL
php-sa-mysql [http://sourceforge.net/projects/php-sa-mysql/]
phpsaadmin [http://www.misak.dk/blog/index.php/archives/category/phpsaadmin/]. For a demo see [http://www.misak.dk/blog/index.php/archives/2005/11/17/41/]
php-sa-mysql2 [http://mail.limelyte.net/downloads/standalone3.0.tgz]. For a Demo of php-sa-mysql2 see http://mail.limelyte.net/webspam/ user test <at> nougen.com, pass test. Notes: php-sa-mysql2 requires register_globals = On, a rewrite is in process.
For Squirrel Mail
There are numerous front ends to Spam Assassin for SquirrelMail, which can all be found at [http://squirrelmail.org/plugins_category.php?category_id=3]
php-sa-mysql-squirrel [http://mail.limelyte.net/downloads/squirrel-plugin.tgz]
user-prefs file generator
Michael Moncur's spamconfig.php: [http://www.yrex.com/spam/spamconfig.php]. This generates a file suitable for download, rather than being a UI you can install on your server directly.