This is the best tutorial I have found that allowed me to install FreePBX on an Ubuntu 14.04 instance on an Amazon AWS instance. I tried a few and this one really did work for me after following all of the steps and exercising patience.
FreePBX is a very useful tool for setting up a free VOIP system for cheap telephony over the Internet. But it must be installed from source so that everything works well together. The only PPA I could find was for Ubuntu Hardy and this is obviously far too old to be practical or secure.