Practical Crocheter wrote last time about a good pattern stitch for making dish cloths, so I thought I'd write a little about dish cloths in general.
Dish cloths and potholders are great small projects. They're portable, versatile, and really useful. And once you've worn one out in the kitchen, it can still be used as a rag for yuckier messes than you would normally use a dish cloth for. I save my old ones for washing the car, for example--which is a lot more discreet than using your worn out underwear.
Anyway, in either knitting or crochet, kitchen fabric is an excellent way to test out new pattern stitches. And this way, those squares get some use rather than collecting in your yarn closet. As long as the stitch is at least somewhat solid, it can be used for a dish cloth. Potholders need to be thicker, so they are best made out of solid stitches, thick yarns, or both.
Practical crocheter made the point that dish cloths are best made out of cotton for its absorbancy, but you can also use corn fiber (if you have some lying around), which seems to soak things up pretty well too. Unfortunately, when cotton gets wet initially it swells up a little, so it is not very good for scrubbing things. For that, I prefer linen (the rough kind), hemp, or really cheap acrylic, the last of which doesn't absorb water at all.
On that note, acrylic is a form of plastic. All synthetic fibers ultimately are. So you can also make a good scrub pad out of strips of plastic grocery bag. And I've heard of people using the tape from cassettes or VHS tapes, but those will degrade faster than other forms of plastic.
Potholders, on the other hand, don't need to be absorbant. They just need to insulate. They are best made out of wool, cotton, and other natural fibers, because plastic can melt. This is especially an issue if you use a gas range and are going to use these things near the oven or stovetop. It's a lot more pleasant to put out a burning potholder than to scrub plastic goo off your stovetop.
That said, I prefer wool for potholders, specifically the kind that can't go in the washing machine. That's because when I want a potholder, I usually opt to crochet it in order to get a thicker fabric. Unfortunately, though, crochet has bigger holes between stitches than knitting does. So I make potholders out of wool and then felt them in the washing machine. It closes up the holes, thickens the fabric, and increases the fabric's ability to insulate. And any animal fiber other than silk will do .
I also think that kitchen fabric is a great way to use up those little scraps of yarn that accumulate from finished projects. I try to keep mine sorted according to fiber, and then use several to make what I need. As long as the fibers are of a similar thickness and behave similarly in the wash, there's no problem with mixing them.