How to get a list of used resources via python? I am able to program simple things in Python but I am not very familiar with Python in Blender. So I would really like to know, if there is a simple way to list all the resources (textures, font files, etc) that are used in the project.?
You should be check and use the API... in this case the data

https://www.blender.org/api/blender_python_api_current/bpy.data.html

https://www.blender.org/api/blender_python_api_current/bpy.types.BlendData.html#bpy.types.BlendData

import bpy

d = bpy.data

## example for textures
textures =  d.textures

for texture in textures:
    print(texture.name)

#example for materials

materials = d.materials

for material in materials:
    print(material.name)