Is it bad practice to have independent Django applications to handle simple one-file components?
I've been do django projects for 4 years. And all I've got from all projects is few ContextProcessors.

If it doesn't do any project-specific operations, I don't see it fitting on any of my project apps, but I also find it to be too small to have an application on its own. Is it?

Just look at this like it's always project-specified until you need it in another project. So my answer is:
Write what you want and how you want. If you need stuff in other place then you'll separate it from project. Don't optimize prematurely.
I've been reading about good practices regarding Django projects management. As I understand, is good to:

Split the project into multiple small applications with specific responsibilities.
Always code thinking in redistributable components.

The second point has become quite important to me since I usually work on more than one project. So whenever I can, I modularize my components into installable packages which I can later reuse.
The question is... to what extend is this a good practice? how should I handle very simple components which are also highly reusable by other applications?
An example would be a simple reusable templatetag, which may be 40~60 lines of code + tests. If it doesn't do any project-specific operations, I don't see it fitting on any of my project apps, but I also find it to be too small to have an application on its own. Is it?