I've tried making liquid detergents, but I really prefer this. It works amazingly well, is super easy to make, and takes up almost no room. It also doesn't contain Borax, which is a rather questionable ingredient.
Powder Detergent Recipe:
1 Bar Castile Soap (I use Kirk's, which is less than $1 per bar. You can buy Dr Bronner's bar soap, but is more expensive.)
1 C Baking Soda
1 C Washing Soda
Optional - Essential Oils of your choice.
Here is the process that seems to work best for me. Using a large knife, chop up the bar of soap. It will kinda flake as you cut it. Then dump the chopped soap and all other ingredients into a blender/food processor/magic bullet and blend until it's all powdery. I always add tea tree oil to kill germs and odor. Sometimes I also add lavender or lemon essential oil as well. The amount of EO you use will depend on how strong of a scent you desire. I personally just fill up a dropper full of each oil.
Use one level tablespoon for normal loads, 2 Tbps for heavily soiled loads. Use 1/2 recommended amount for HE washers. This is a low suds detergent and works very well in HE machines.
btw, I do this in my garage, or put a bag over the food processor, cause the powdery stuff makes everybody really sneezy.
Washing Soda. This should also be in the laundry isle. It is hard to find in some places.
You can use just about any kind of bar soaps for this recipe. A castille soap is going to be your "greenest" choice.
For fabric softener, use white vinegar in the rinse cycle. It naturally softens & removes build-up. Use about 1/2 cup per load. I just use a downy ball. You can also add a few drops of your favorite essential oil for fragrance. Even if you don't add a fragrance, your laundry will NOT smell like vinegar.
You can buy essential oils at any natural foods store. I use a lot of EOs, so I usually buy them online. My favorite place to order is Mountain Rose Herbs. http://mountainroseherbs.com/ They are great about ensuring that their items are harvested and produced ethically. They also have a wonderful rose petal tea. Mmm... If my budget is tight, I will order from Wholesale Supplies Plus http://wholesalesuppliesplus.com/