I use moreniche. Please use my link if you decide to take a look.
http://track.moreniche.com/join.php?w=236840&campaign=mf (I think I've understood that it's ok to post it as it's in context to the post)
They have products in the health, beauty and weight loss niches and their sister site impact5 has men's health products. The commissions are very good, typically around 30% often more.
They are very user friendly and helpful and there is a wealth of excellent information there for anyone who's just starting out. They also have a great forum and very helpful managers. I've looked at a few affiliate programmes and this is by far the easiest to use.