This module allows you to add a mathematics filter to your regular input filters. You can then post mathematical equations between [tex] and [/tex] tags. You can also post mathematical graphs between [graph] and [/graph] tags (or the slightly more complicated format [graph xmin="#" xmax="#" ymin="#" ymax="#"] x^2+4x [/graph] where the # should be replaced with appropriate integers.) . The mathematical equations relies on the Mimetex binaries created by John Forkosh available as a separate download from here. Documentation on what types of graphs are able to be presented are available from here.
Note: The Drupal 6 version of this has critical bugs and needs to be properly upgraded before it should be used.