HAProxy best practices - require its own server?

I just finished reading Scaling PHP (http://www.scalingphpbook.com/). Tons of great information. My question is about HAProxy. Does it need to be its own dedicated server and can it be ran for load balancing website and MySQL as well? Just curious of best practices for HAProxy.

If anyone could describe their set ups with HAProxy and or provide a good online resource with more information, that would be awesome.