Recently we've taken a look at the many different animal fibers that you can crochet with as well as the many different plant fibers that have been turned into yarn for crochet. You can basically crochet with anything that resembles string; it doesn't have to be a fiber at all.
Fabric can be turned into thin strips and connected together to create beautiful yarn-like material that is used for crochet.
In recent years it's also become widely publicized that you can turn plastic bags into yarn. This "plarn" can be used to make a wide range of different items. One common charity use is that people use "plarn" to create sleeping mats for the homeless.
Wire crochet is commonly used to create beautiful jewelry. You crochet with very thin wire in the same way that you crochet with yarn. Wire crochet can be used to create other items besides jewelry, like wire crochet lamps.
Very few people have mastered the art of crocheting with glass, but believe it or not, it can be done. Artists like Catherine Carr have perfected the art of making glass crochet items.
5. Paper / Newspaper
Almost any kind of paper can be turned into a yarn-like fabric if you're patient enough to work with it in a way so that it doesn't tear.
Ivano Vitali has proven as much with his newspaper crochet fashion.
6. VHS / Cassette Ribbon
Head to a local thrift store or yard sale and rescue a handful of old VHS tapes or cassette tapes from the bargain bin. Pull the ribbon out of those tapes and use it like yarn to create beautiful upcycled crochet items.
It's a little bit stiff, so it's great for making durable items like vases and vessels.
I imagine that it's really difficult to crochet using balloons as your material, but it can be done, as artist Olek has proven it.
Laurie Wheeler writes, "From licorice ropes and cooked spaghetti, intrepid crochet lovers have made projects that amuse and inspire other crocheters to take it one step further in the quest to find unusual 'fibers.'” She herself has crocheted with bacon.