I always run a load through the washer void of clothing with a good bit of scent free detergent before actually throwing my clothes in.

I know this doesn't completely rid the washer of the other detergent smells, but it definitely [read; probably] knocks it down a bit.

As for the dryer, I throw a fresh earth fabric softener sheet in there and it definitely comes out smelling like dirt. Throw it directly into a Rubbermaid container with fresh earth and pine wafers and I'm smelling like a forest when I get dressed.