Coming from #681034-6: Download Mechanism,
I just realized that it won't work forever to point new people who would like to help to existing issues and have them read them.
I guess that, thus far, the essentials live in the following isues:
1) The original #320562: Libraries API (Wysiwyg), initial considerations, bound to editor libraries only (but even with that limitation already a challenge).
2) #315100: Allow to add JS/CSS libraries (sets of files, settings, and dependent libraries) (Drupal core) also holds lots of details about the challenges of handling external libraries; thus, that core feature is not to be mistaken with Libraries API. (perhaps we should clarify this much further on the project page, too)
3) #719896: Add a hook_libraries_info() (Libraries), most recent considerations.