I bought a set of Dryer Balls a few months back to try out in the laundry. So far, so good. They work almost as well as a regular dryer sheet (90% effectiveness) and I don’t have to pick up dryer sheets from the store anymore.
The biggest reason that people buy these things, though, is that they are supposed to be environmentally friendly. The idea is that by using the blue rubber balls instead of dryer sheets you are  saving trees from being cut down to make the sheets, and  saving the toxins in the fabric softener from entering the watershed (either upon the next wash, or upon disposal of the sheet).
Turns out, there are some additional negative side effects to the things. According to treehugger.com:
What the manufacturers fail to mention, however, is that the the polyvinyl chloride (PVC) material the supposedly “nontoxic” dryer balls are made of is one of the most poisonous plastics ever created, posing great environmental and health hazards in its manufacture, product life, and disposal.
Yet another green alternative that ain’t that green. The unfortunate part of the current green movement is realizing that nothing we do really has a small impact on the world around us. Maybe one product is better than another during it’s lifecycle, but what about upon disposal, or during manufacturing? Perhaps the product is a traditionally poor product for sustainability, but it’s sourced from better materials than others.
Doesn’t hurt to keep trying though.
I figure I’ll keep the dryer balls I have for now – I can’t see any evidence that using the product is harmful, only manufacturing and disposal – as I figure it’s better to keep using it now that it’s been made and purchased. If anyone else is considering something similar, that’s a canadian product called Fluff Balls that are supposedly a little better. They are made from wool. Don’t let the website fool you, they are actually about $25 for purchase.
Also, some people have reporting getting good results from tennis balls.