From the Guardian: Food and health firms taken to task over sales pitches by science's 'warriors against claptrap' reports on the release of There Goes the Science Bit..., Sense About Science's dossier of scientists' experience in demanding scientific evidence for product claims.
Products include a Nutridirect Parasite Cleanse (which plays to users' parasite fears); Activ8 yogurt (for the claim of "proven to optimise the release of energy from our diet"); Computer Clear (which purports to use "bioresonance patterns" to protect computer users against electromagnetism); Champney's Detox Patches (one of the many incarnations of foot detox patches - see More pseudoscience afoot); Pret a Manger (a sandwich firm playing the "natural" card); the Co-op and Sainsbury's, for removing some additives on the basis of consumer concern rather than scientific evidence of risk; Q-Link (a pseudoscientific device said to protect the wearer against electromagnetic radiation); Aerobic Oxygen, a liquid with alleged purifying properties; Salt Lamps (allegedly healthful rock salt lamps); and Clarins Magnetic Defence Complex (recently slugged by the Advertising Standards Authority).
The dossier is available as a PDF download here. It's a good model for how to make life difficult for promoters of pseudoscience. Other ways you might consider are the ASA, which regularly upholds complaints on such grounds, though it unfortunately doesn't cover companies' own websites; and local Trading Standards offices. An area where they take an interest, for instance, is companies making statements in breach of the 1939 Cancer Act, which states "No person shall take any part in the publication of any advertisement ... containing an offer to treat any person for cancer, or to prescribe any remedy therefor, or to give any advice in connection with the treatment thereof. This BMJ letter mentions successfully invoking it, as does British company fined for falling foul of Cancer Act.