How To List Packages From A PPA / Repository In Ubuntu

A few weeks ago, we saw how to find out to which PPA / repository a package belongs to in Ubuntu / Debian. But how about getting a list of packages available in a PPA / repository?
There used to be an option in Ubuntu Software Center that would list all the packages available in each PPA added on your system, but it was removed. However, you can still do this either using Synaptic, a command or using Y PPA Manager.