We currently use a module that allows you to include LaTeX-style equations in all of your posts. Simply surround your LaTeX commands with the [tex][tex][/tex]...[tex]\[/tex\][/tex] tags and when the page renders, you will see the mathematics rendered as small images.

Some examples of LaTeX commands are as follows:

[tex][tex][/tex]\frac{x}{y}[tex]\[/tex\][/tex], rendered as [tex]\frac{x}{y}[/tex]

[tex][tex][/tex]\sum_{i=1}^N x_i[tex]\[/tex\][/tex], rendered as [tex]\sum_{i=1}^N x_i[/tex]

[tex][tex][/tex]\int_{t=0}^1 x(t)dt[tex]\[/tex\][/tex], rendered as [tex]\int_{t=0}^1 x(t)dt[/tex]

Please see the MimeTeX webpage for more examples.