NOTE: If you're just coming here to explore adding Gantt charts to your Feng Office installation, you only need to read the first two posts in this thread to install the latest code, with the latest instructions. All the other pages of posts are discussion about improvements and bugs that are then fixed ASAP and posted back to these first two posts... There may be some idiosyncrasies between MySQL or PHP installations that can't be resolved however, and the additional pages of posts might help you in that regard.
Let's begin...
As you know, we need a way to make Gantt charts from Feng Office, and we looked for several weeks at different avenues. Google Visualizations, FlashCharts, java scripts, etc. All had severe limitations - not printable, not feature-rich enough, required non open-source or non-free software, etc.
We finally settled on integrating the free jsGantt javascript into Feng Office. It requires the creation of a few views in MySQL which we will provide, and that is about it. The jsGantt feature does not have to be loaded into a tab in Feng Office if you do not wish to do so, but we opted for it as it gave a more "one-stop-shop" feeling for our users.
We have made what we consider minor improvements to jsGantt, but they are not material to its function, and it will work just fine in its base form if you download it from jsGantt.com. The version referenced here is 1.2, and it looks like this:

There is a data-selection form which appears on the Feng Office tab and which allows you to select one or more workspaces, and/or one or more users to determine what will be charted. You may also optionally specify a start and end date for the tasks that will be included on the chart, whether to inherit colors from the workspaces, and whether or not to display percent complete, duration, start/end date, and resource for each task.
Tasks in personal workspaces are never included.
Clicking on a task or milestone that is assigned to someone will also open a new e-mail address to that person, and with the task name as the subject.
Step one, if you decide you want to integrate the Gantt chart onto a tab, will be to follow the steps oulined in the "Hello World" posts in this forum and elsewhere, to give the Gantt chart a place to live within Feng Office. Otherwise, you may just as easily reference the Gantt chart as part of the same or even a separate website from Feng Office, it only needs access to your Feng Office database.
I've outlined the steps I took to integrate the tab in a message later in this thread, which you can access here -
http://forums.fengoffice.com/index.php?topic=3826.msg14312#msg14312.