Thoughts from a 21st century educator.
To create equations with Movable type, you need 2 files uploaded to your Movable Type site.
1. The 'textags.pl' file (modified from QuickCode created by Crys Clouse) in a folder called 'TexTags' in your plugins directory.
2. A version of 'mimetex.cgi' (or the equivalent) appropriate for your server type. For different versions of this file, see http://download.moodle.org/mimetex/
What you do is upload your version of 'mimetex.cgi' file to your Cgi-Bin (making sure to have the permissions appropriately set, chmod to 755 works fine). Next you open up textags.pl with a text editor and modify the line (about line 30) that points to your mimetex.cgi file so that it points to the appropriate location on your server. Note that the ? at the end of the location is extremely important. Also note that if you know a bit of PERL you may notice a bunch of commented lines that look similar to this line. If you want to enable any other tags, just uncomment the appropriate line.
Next you upload the 'textags.pl' file to a folder inside your plugins folder. This folder and this file should also both be chmod to 755. The name of the folder is not crucial, but something self explanatory like 'textags' is probably a good idea.
Now you need to enable the 'text formatting' options for your entries, so you can choose 'TexTags' as an option.
You should test out your installation by trying out some of the examples at John Forkosh's website (see http://www.forkosh.com/mimetex.html).
If you are unable to install your own version of mimetex.cgi on your server, you can leave the path alone as it points to a public version of mimetex.cgi. However if it is at all possible to change the path, I would do so, as we do not want to overwhelm this public mimetex.cgi file.
Thanks go to John Forkosh for developing this Mimetex alternative to Latex and to Crys Clouse for providing an excellent Movable Type plugin.