The following sites all offer free samples of their towels. The first two are for anyone to request; the last two are more specific.
I.M. International
Just fill out this short form to request a free guest towel from I.M. International. Or, with Christmas approaching, perhaps you'd prefer a free Christmas gift towel, which they are also giving away. (You can expect to be marketed to afterwards; both forms require your phone number.)
Cat's Tongue
Cat's Tongue is giving away samples of their Heavy Duty Cleaning Towel -- but you do have to request it through the mail and pay shipping. (Currently, that's a mere $0.60.) See the website for full details. With your free towel, you'll also receive some discounts on future purchases.
Charm-Tex
If you run a facility that uses towels and/or bedding, Charm-Tex will send you some free towels to try. You'll need to provide some information about your facility and also tell them which style(s) you are interested in.
Zeza
If you're in charge of purchasing for a hospital or other medical facility, Zeza has a free sample pack of various surgical towels that you can request. The pack includes large disposable towels, a surgical drape, and more.
