As much as I'd like to push a Firefox agenda, I went looking for a bitmap solution, since that would ensure everyone sees the same thing with wide compatability. I found LatexRender
which I have put up for testing at http://www.bentest.dreamhosters.com/bb
. Forum password is polywell
Note, that is not my normal webhost and the trial account may expire on the 18th April. I tracked down talk-polywell.org to be hosted with dreamhost.com, and their plan was fairly attractive (see following post) so I thought I would try it out. Testing on their system should make it easier to then implement on talk-polywell.org, so I signed on for a two-week trial, set up phpBB and installed LatexRender. Fairly straightforward. You might want to try a free trial yourself
For anyone wanting to use LatexRender with pbpBB on DreamHost, here is what I did: (with the bold bits needing to be customised for your account)
 From the DreamHost Panel, Enabled Shell Access. Used Putty application for MSWindows to SSH into the dreamhost server.
Alternatively you could unpack/edit files locally and FTP them.
$ mkdir tmpinstall ; cd tmpinstall
$ wget http://www.mayer.dial.pipex.com/latexrender.zip
$ unzip latexrender.zip
$ cp -r ~/tmpinstall/phpBB/latexrender ~/bentest.dreamhosters.com
$ cd ~/bentest.dreamhosters.com
$ vi latexrender/phpbb_hook_2.php
Edited according to README_phpBB3.txt (although talk-polywell.org may require README_phpBB2.txt instead)
< $latexrender_path = "/home/coman/bentest.dreamhosters.com
< $latexrender_path_http = "/bb/latexrender";
< var $_image_format = "png"; //change to png if you prefer
(since gifs were pixelated)
$ vi includes/bbcode.php
Edited according to README_phpBB3.txt
 In the phpBB Admin Control Panel, added a new bbcode tag.
As described in README_phpBB3.txt
Thats it for phpBB3. (although there is a bit more to do for phpBB2 that talk-polywell.org runs on)
Hope that helps.