MathJax
You can enable MathJax by setting mathjax: true on a page or globally in the _config.yml. Some examples:
Euler’s formula relates the complex exponential function to the trigonometric functions.
\[e^{i\theta}=\cos(\theta)+i\sin(\theta)\]The Euler-Lagrange differential equation is the fundamental equation of calculus of variations.
\[\frac{\mathrm{d}}{\mathrm{d}t} \left ( \frac{\partial L}{\partial \dot{q}} \right ) = \frac{\partial L}{\partial q}\]The Schrödinger equation describes how the quantum state of a quantum system changes with time.
\[i\hbar\frac{\partial}{\partial t} \Psi(\mathbf{r},t) = \left [ \frac{-\hbar^2}{2\mu}\nabla^2 + V(\mathbf{r},t)\right ] \Psi(\mathbf{r},t)\]Code
Embed code by putting {% highlight language %}{% endhighlight %} blocks around it. Adding the parameter linenos will show source lines besides the code.
staticvoidasyncEnabled(Dict*args,void*vAdmin,String*txid,structAllocator*requestAlloc){structAdmin*admin=Identity_check((structAdmin*)vAdmin);int64_tenabled=admin->asyncEnabled;Dictd=Dict_CONST(String_CONST("asyncEnabled"),Int_OBJ(enabled),NULL);Admin_sendMessage(&d,txid,admin);}Gists
With the jekyll-gist plugin, which is preinstalled on Github Pages, you can embed gists simply by using the gist command:
Images
Upload an image to the assets folder and embed it with ). Keep in mind that the path needs to be adjusted if Jekyll is run inside a subfolder.
A wrapper div with the class large can be used to increase the width of an image or iframe.
Flower by Tj Holowaychuk
Embedded content
You can also embed a lot of stuff, for example from YouTube, using the embed.html include.