They can be used for snaring birds whilst falling from a three-mile high marble statue.

They can be used to signal temporally unstable spaceships by fossilizing them in planetary strata.

They can be soaked in nutrients to provide sustenance in awkward situations (Although, as Zaphod Beeblebrox found, this is not a terribly tasty solution to hunger).

They can also do a really good job of drying between your toes.

The Hitchhiker's Guide is full of suggestions for successful towel deployment. It is worth noting that a cup of white vinegar in a wash will help keep your towels fluffy and soft.