I was in the greenhouse of a local garden center and came across these plant labels from Ferry Morse the other day. The price is pretty steep when you consider that they're just thin pieces of plastic and you could easily make your own plant labels to keep track of your growing houseplant collection or the seeds you start making mini greenhouses out of used soda bottles. You can make something similar and just as useful by cutting the tops and bottoms off of your gallons of milk or soda bottles and cutting the sides into strips.
If you have kids around then you probably buy a lot of Popsicles and throw away a lot of the wooden sticks. Rinse the sticks off and set them aside to dry and then you can use them as plant labels. Or you could buy a bag of the wooden sticks in crafts stores or dollar stores in your area. A local dollar store sell them 100 sticks for a dollar which is a lot cheaper than these cost.
Don't throw away your mini-blinds as they can also be cut up into strips and be used as plant labels. One mini-blind can produce hundreds of plant labels that could last you for a very long time. If you aren't redecorating your home check out any junk shops or garage sales near you for used mini-blinds, they can easily be cleaned and serve a purpose in your garden instead of taking up space in landfills.