TWiki is a flexible, powerful, and simple Web based collaboration platform. It is suitable for dynamic intranets and knowledge bases, and for sharing and managing documents and collaborative projects. It resembles a normal Web site, but every page can be changed from a browser. It features automatic link generation, full text search, group authorization, Web forms, reporting, change notification, file attachments, revision control of pages and attachments, a modular templating system with skins, hierarchical navigation based on the topic parenting feature, and more. Plugins can be used to enhance the program and build groupware applications.
OTRS is a platform independent Web-based help desk system that supports service organization of any kind (e.g. IT service, customer and technical product service, complaint management, public services, etc.) to increase their efficiency. It increases transparency as well as service quality and lowers your total cost of ownership. It has been certified ITIL V3 compatible by PinkVERIFY for incident, problem, change, service asset and configuration, request fulfillment, and knowledge management. Other ITIL processes like service catalog and service level management are supported as well.
Gutuma is a feature rich PHP newsletter/mailing list management tool that is designed to be easy to install and use. It doesn't require a database, yet offers multiple lists, import and export from CSV, file attachments, drafts, AJAX subscribe gadgets, administrator email notifications, MD5 protected logins, and batched deliveries that can be driven by a cron job.
CGI::ContactForm is a Perl module that generates a contact form for the Web and sends a message to a predestinated recipient. Unlike many form-to-mail programs, it's limited to this single purpose, but it allows you to set up a decently designed form with a minimum of effort. In other words, it's simple to use rather than flexible, even if there are quite a few customization possibilities.