LaMark allows LaTeX equations to be inserted into Markdown documents. For example: 1

The footnote was also generated using a LaMark tag.
Of course, more complicated formulas are possible:2

If you like, you can also embed arbitrary LaTeX using the {%latex%} tag. For example: 
Once the the document has been written, running it through the LaMark processor is easy:3
lamark -f demo.md | ./Markdown.pl > demo.html
.