You could get a piece of cardboard and cut Mirco SD sized holes into it and then write what each one is above or below its respective hole.
You'd need to put a backing on the card so that the SD cards don't just fall straight through if you try and pick the board up - try something like another sheet of cardboard or even paper, if you're looking for a more protective solution, do the same with Styrofoam or something similar (however Styrofoam is prone to static build up and could lead to the SD Card being damaged or destroyed).
You could also put the cut out into a small plastic cover (something like a normal SD card or an old Game Boy game case) which would then keep them all sorted and all in one place!
Here's a link to instructablesinstructables where I was able to find something similar to what I am describing.
If that doesn't do it for you then you could invest in something like a small fishing box with lots of small compartments and have one compartment for each SD Card - might be a bit over the top for such small devices but it is up to you!