I wanted to take a quick look at felting in this post. I've made a few felted bags and hats in the past, and always have fun. You can make hats, bags, hot pads, cat/dog beds or mats, and lots more.
I have never followed a pattern, but rather just cast on, knit, and then felted. My projects have always turned out well. Luck, I guess!
I made a short video of how I felted the piece of knitting above. My typical method is to just run my project through the wash with a small load of laundry, using hot water and a short to medium long cycle. Rarely do I stop the machine to check progress. I do recommend you check your item about halfway through to see how it is coming along. The old 'Do as I say, not as I do' bit. If my item is not felted enough to my liking, I leave it in for another round with the next load. The yarn is some that I dyed myself. It started as a neutral/ivory color, from Patons. I forget the needle size used, sorry. I cast on 34 stitches, knit for about 50 rows. This was about 7.5 x 5.5 prior to felting. It came out at about 6 x 5.
Place the item you want to felt into a pillow case. A lingerie bag is sometimes suggested, but the lint/fuzz can still get out of the bag, and if you felt a lot, the lint will build up and ruin your machine. A pillow case will collect most of the lint.
You can just throw in a pair of jeans or two to help agitate your project and help the felting process. Don't use new jeans though, because the color could bleed and get onto your project. (You know, like when you accidentally put a new red T-Shirt in with something white....) Better to use old jeans.
Some people suggest using towels - I do not. Towels give off lint/fuzz pills of their own, particularly if they are newer, and it could stick to your project. Older towels may not pose much of a problem, so you may be fine to use old towels.
Detergent helps the felting process, so if you are washing some laundry, of course you will already be using some. If you are just felting with a pair of jeans or two for the agitation, go ahead and put a small amount of detergent in.
Not all yarns will felt in the same way. Some may felt faster than others, some may shrink more or less. Your best bet is to knit up a test swatch and felt it to see how the yarn reacts. You will need to use an animal fiber for felting, as acrylic yarns will not felt. Animal fibers have scales, which open up when exposed to hot, soapy water; with agitation, these scales become tangled together. The scales close up and remain locked together as the fiber cools down and dries, creating felt.
You may have some difficulty felting white yarn; sometimes these yarns have gone through a bleaching process, which removes the scales from the fiber. No scales, no felting. Again, your best bet is to do a test swatch, or even ask around for advice from frequent felters. Try the boards at Knitting Paradise, for example. Interweave has some felting magazines, and there is even an Australian magazine called Felt you may want to check out.
A few links:
Knitty - Felt This
How To Felt
Books:
Felting - The Complete Guide
Uniquely Felt
Knitting Never Felt Better (Nicky Epstein)
And of course, the famous Booga Bag by Julie Anderson of Black Sheep Bags!
Here is a cute little bag I made several years ago. I also did one in pink. The yarn is some that I purchased on eBay from forestgreener. Great seller that I have purchased from often. I always love the yarn, and have never had a problem with this seller. There is no pattern for this bag; I encourage you to create something unique for yourself.
Here is the video. Happy Felting!