I'm going to try that shampoo idea! Rowan's method which he linked to sounds good, but quite onerous for those with long chains (i.e. Xtracycle and recumbent riders).

Baby shampoo, IIRC, is thin enough to penetrate the cracks but thick enough to cling to the chain. A strong blast of water should be sufficient to remove most of the grime from inside the rollers. If not, it's a chain. It'll break eventually anyway.