I just joined markethealth awhile back too. I was really impressed with all of the stuff that they had for their affiliates to use in their promotions. The downloadable sites are a nice bonus.
I've just launched a weight loss eBook and I pay 75% in commission which means you earn $37 for each sale you make. It's through Click2Sell which is free to join and I'll be able to pay you within 1-2 days directly to your PayPal. Have a look at my sig if you want to bank in on the weight loss niche.
I personally recommend MoreNiche. Currently only has three health products, but many more are on the way. Plus of course the resources and help available in my opinion is well worth it.
I think moreniche affiliate is best also Click bank also good. I am using moreniche for affiliate and it's good one for me. I have just taken 2 products for promotion, but not more success, but moreniche products are effective and we can generate sales of moreniche products.
I've bookmarked this site for myself, since I found that it is profitable health product system in the future..! It is presented by World famous Multimillionaire TV Doctor..! She is going to give you a complete fully-operational Website that sells the absolute very BEST proven health-related products online in a Web-Business of your very own.. Check it out... >> Health Biz In a Box <<