My eldest son recently went to the dentist for a regular check up, each time we go to the dentist, we get a new toothbrush at the end of the visit. I love that!
But what do I do with my old toothbrushes? LOTS!
I keep one in my kitchen to use on the rim of my sink. now, I wash, with a cloth, the inside of my sink and around the edge of it every time I finish washing a load of dishes - and with five people in our family, dishes are washed a lot!
But, no matter how often I run my cloth along that edge, crap gets stuck under the rim of the sink. I hate it. If I had the chance, I would buy and install an undermount sink, that's the kind where the edge of the counter goes right up to the opening of the sink, there is no rim for crap to get stuck in.
SO. Do not ever through out an old toothbrush - they work on sinks, the runner that the windows are in, I even keep one separate for helping me scrub dishes! (A toothbrush will clean a cheese grater in seconds!!)