Pinlock Faceshield Inserts: $30 (and up); pinlock.nl
Whether it's rainy, cold, or you're just panting from a quick lap at the track, the inside of your visor fogging is a pain. There are three options: 1) don't wear a helmet (not recommended), 2) crack your visor and hope it doesn't get worse, or 3) get a Pinlock. It's made of moisture-absorbing plastic, silicone, and magic. We use them all the time, and they're awesome.