For tagging plants I cut up a cheap window blind and use the plastic slats, you can cut them to the length you want. I write on them with a Sharpie and stick them in the soil, with the writing under the soil so the sun does not fade it.
Or you could write on the boards of your raised beds with a Sharpie.
Ah there ya go, that would surely work. Good idea, I actually have some old blinds I am going to get rid of.. so that may just be what I need.