It is possible to create Gantt charts on the wiki using an XML based project plan description.  Instructions are here:
[[http://www.logilab.org/projects/pygantt/documentation]]
and
[[http://moinmoin.wikiwikiweb.de/ParserMarket/Gantt]]

Note: I've removed this feature for now, since it is extremely difficult to use.  You have to painstakingly edit an XML file to create the chart and there is no GUI.

{{{#!Gantt name=CytoscapeReleaseSchedule,
<project xmlns:pg="http://www.logilab.org/namespaces/pygantt_docbook" id="monprojet">
  <label>Cytoscape</label>
  <task id="module">
    <label>Testing</label>
    <task id="func1">
      <label>Code Freeze</label>
      <duration unit="days">1</duration>
      <constraint type="begin-after-date">2005/08/15</constraint>
    </task>
    <task id="func2">
      <label>Testing</label>
      <duration unit="weeks">4</duration>
      <constraint type="begin-after-date">2005/08/15</constraint>
    </task>
  </task>
</project>
}}}