I can't tell you how many times people have recommended I start carrying a portable black light with me on the road. Useful as it may be to detect those unmentionable mattress deposits left by former guests of motels I happen to stay at, I prefer not to think about it and just take a nice long shower in the morning.
If it's something you find just too jeebie to get past, though, I've come across an alternative you might want to look into. Called the TravelFresh Sleep Sack, it's like a full-body, cotton-blend condom made specifically for motel stays and designed to protect you from both foreign fluids and biting bedbugs.
Just slip it between the flat and fitted sheets and crawl inside. It measures 43 inches by 93 inches — larger than an average adult-size sleeping bag — but folds into a pouch no larger than a pair or two of socks. Plus, it features a built-in pocket into which you can slip a motel-provided pillow, so you don't have to schlep your own.