There are loads of recipes on the internet for home made laundry detergents, this is the one that I use I can't quite remember where it came from. I have made a few batches of it and found that it works really well and because its a liquid it can be rubbed neat onto stains. The best thing is it is incredibly cheap to make.
All you need is soap flakes, washing soda and borax. I managed to buy soap flakes and washing soda in Waitrose and ordered the borax online although I have since discovered that they sell it in Robert Dyas. I've made about 4 batches of liquid so far and still have plenty of the ingredients left.
You first need to dissolve 1 cup of soap in 1 1/2 litres of water, I have found this is best done by slowly heating the mixture while stirring with a whisk, (I know there is a spoon in the picture I took it before I discovered that the whisk worked better.) You need to make sure that all the soap dissolves, when it has, remove from the heat and add 1/2 cup of washing soda and 1/2 cup of borax.
Then you need to dilute the mixture with hot water from the tap. I have a builders bucket that has measurements marked on the inside, it was 99p from the diy store, I pour the mixture into it and top it up to the 10 litre mark, stirring with the whisk the whole time.
I decant the liquid into 2 litre drinks bottles, you need to let it cool down first. It goes quite thick when it cools and can sometimes separate a bit I just give it a good shake before I use it.
I have a cup from the top of an old flask that I use to measure it out, we have very hard water here so you could probably us less in an area with soft water. I gives the washing a nice fresh smell, although sometimes I add a bit of lavender oil to the softener compartment if I want a bit of fragrance.