I would like to learn to create a Linux package from source. I would like to create package for CentOS, but maybe I could ask a more generic question.
Where is the right place to ask this?
The Unix & Linux Stack Exchange site is probably the best place for specific questions about Linux packaging.
(Of course, if the question is mostly code-related, it probably belongs on Stack Overflow instead. And be sure to formulate a specific question about a problem you're having, rather than asking a vague "How do I package things for Linux?" type question...)