If you do not wanna spend the money or have no time for tools like Texturemaker and similar go to this site. They offer you (nicely catalogued) some (more than 1000) textures with normal and bump derivates, exactly like the Blender users needs them. It’s well organised with an ad-free layout like OPEN SOURCE pages. Of course they advertise for their own product.
that is a seriously cool website…! pluss the normal maps look like they should be correct…
apparantly they GLSL shader that change over distance… including the normal maps… all by just using a GLSL shader…