An overview of what belongs in each directory of a Vim plugin.

vim-plugin-directories

plugin
    naming convention: name_of_plugin.vim
    these files are sourced for all file types

doc
    naming convention: name_of_plugin.txt
    these files document the functionality of a plugin

color
    naming convention: name_of_colorscheme.vim
    these files define a colorscheme for syntax highlighting

syntax
    naming convention: filetype.vim
    these files define the operators, keywords and constructs of a language
    the syntax groups defined here are used by the colorscheme
    (much like HTML elements, ids and classes provide hooks for CSS styling)

indent
    naming convention: filetype.vim
    these files define the `indentexpr` for a language
    the `indentexpr` is used by the `=`, `o` and `O` commands

ftplugin
    naming convention: filetype.vim
    these files are sourced only for the specified filetype
    suitable for defining functionality for one particular language
    e.g. a command to build an HTML document from a markdown source

autoload
    naming convention: ???.vim
    Vim provides a mechanism to ensure that startup time isn't compromised 
    when large scripts are loaded. Functions, commands and mappings defined
    in the autoload directory are defined with an empty implementation on
    startup. It is only when these commands are invoked by the user that the
    script is sourced in full, and each command is attached to its
    implementation.
    :help autoload-functions
    :help 41.14

Glad it helped. You're right, it might be worth turning this into a blog post.

It might be useful to add the "after" directory, and a note about how it contains a clone of this structure but is loaded after other scripts. In fact I'm not too sure about this myself, so an update here would be good.

+1 for after directory.

some personal opnions :)

1. :help 41.15 to check autoload functionality
2. dir color should be colors
3. add dir ftdetect compiler

Big thanks for this.

+1 for after directory.

just curious, does the same directory structure works with neovim?
I am thinking about totally ditching .vim/ direcectory and move everything to .config/nvim/.

just curious, does the same directory structure works with neovim? I am thinking about totally ditching .vim/ direcectory and move everything to .config/nvim/.

Yeah, you can do that. Check :help vimfiles to see all about it. :)