Another tip for vinegar (told you I liked the stuff). I think I picked this one up from Shannon Lush. Shannon does a segment on ABC Local Radio helping people with their cleaning problems. She's got a couple of books published. I don't own any, although I did buy one for my defacto dad as a joke (he's a perfectionist cleaner - something I'm not).
Anyway, the tip. Towels should never be washed with fabric softener 'cause it stops them being effective water soaker-up-ers. But, most of us hate scratchy, hard towels. The answer is to use vinegar instead of softener. I just pour it in the softener holder in the machine.
As mentioned before vinegar helps kill mould, so it helps clean the insides of your machine at the same time.
A word of caution, however, I read somewhere that some machines don't like vinegar. It apparently attacks some of the soft fittings. I haven't noticed any problems with our machine though.