dotProject
Powerful open-source web-based project management application that is the perfect solution for those looking to collaborate and manage projects. Similar to MS Project, this system allows you to use the web to everyone in sync and up to date one every project.

Help Center Live
Add live help to your website with this handy application. Not only can you provide live help, but it also comes with support tickets (OS Ticket) ability to create multiple departments and users, and gives you the ability to track in real time visitors as the navigate through your website.

netOffice
NetOffice is a simple to use project and client management system for tracking project tasks and deliverables. The key features are its simple design and administration, as well as a special client module the gives clients an updated view of their projects, while giving your the flexibility to only display information you want.

osTicket
OS Ticket is a state of the art support ticket system designed for small business. Supports both web form ticketing and email piping and a host of features to make one of the best systems available for the price.

phpBB
One of the most widely used forum solutions, phpBB has an easy to use administration panel which allows you to have a forum set up in minutes. It is highly customizable with a great set of features that will complement and grow your website

SugarCRM - Community Edition
One of the best web based customer relationship (CRM) applications available today, SugarCRM community edition provides all of the top of the line features found in high end systems hosted by CentrioSolutions at an affordable price.

TikiWiki
TikiWiki CMS is a full-featured, web-based, all-in-one Wiki, CMS, and Groupware application. TikiWiki offers a very large number of features and is highly configurable.

WebCalendar
Needing a web based calendar with lots of functionality? WebCalendar is for you. Loaded with lots of features such as permission based access. Meeting updates and group setting, WebCalendar is the perfect way to keep a group or team Calendar.

WordPress
If you plan to start your own blog website, the best choice for a blog application is WordPress. This application has an intuitive easy to use administration tools which makes it easy to compose, post, and publish your blog with just one click!