Borax works very well, as does lemon scented dish washing detergent (Lemon Fresh Dawn is the champ). You cannot put dish detergent in a washing machine because it foams like crazy and can damage the pump, but a presoak in a tub with a bit of hand agitation, followed by a rinse and normal machine wash works very well.

There's also a product called sink the stink sold in dive shops, which is made to de-stink wetsuits which are probably the world's champs at getting funky.