These two articles seem to discuss many of the commonly discussed points about natural worming:
There is a fair amount of similar information on the Web. I have not tried the products other than DE myself (or on myself, for that matter). I'm not too sure about the mode of operation of DE that the author mentions, but she could be right. Your vet probably told you this, but it's best to isolate the treated cat from the untreated/infested ones, lest the untreated ones re-infest the treated one. It can happen fairly easily. I don't believe that the Prairie View A&M College study on using DE on goats that the Dirt Doctor mentions in the Organic Research part of this Web site addressed tapeworms, but my memory is a little vague on that. If I find out different, I'll post it. There probably is plenty more about natural wormers, and there is more on DE in the Organic Research section, so ohers may add to this.