I use vinegar instead of softener. It started when we were using cloth nappies for the baby, as you are not supposed to use conditioner on them (it means they are less absorbent - not good for a nappy!). The same is actually true for towels, altough I only found that out later.
Just put a good slug into the conditioner section of the washing machine and wash as normal. I was filling up the container, but when I was almost out, I reduced the amount to just a couple of good squirts (the amount for maybe 2-3 plates of chips!!) and it worked fine. They come out lovely and fresh and still quite soft. I rarely use commercial conditioner now.
I also found that you can add a couple of drops of tea tree essential oil to the wash as well. (With or instead of the vinegar). This is a great antiseptic for clothes, but it also leaves them smelling nice too. I sometimes add a couple of drops of tea tree and a couple of drops of lavendar oil (really lovely on sheets, as it helps get relaxed for sleep).