I use the NuvaRing and I think it's great. It has much lower doses of hormones than some other forms of BC, since it is delivered right to the source, as it were. (It's a plstic ring worn in the vagina for 3 weeks, then it's out one week, then you put a new one in.) I can't tell I'm wearing it, and my husband has also not noticed it either - although if the idea of having sex with it in makes you uncomfortable, it can be removed for a few hours, without rendering it ineffective. (They have a website with all sorts of FAQs and stuff about that.)
Just my two cents on natural family planning/rhythm methods, etc. It can be highly ineffective for some women, and not because they aren't following it 'properly'. Some women, scientists have discovered, are fertile just about all darn month. Also, women with less than clockwork-like menstruation schedules may find it impossible to follow with any certainty. In the 1950s, when there were debates in front of the Senate about the availability of birth control, there was one woman who testified about using natural family planning. She had such a hard time with it, she and her husband would abstain for months on end, to try to figure out her cycle. She ended up with 13 children.
It's great that it works for some people, but if you are in a position where you really don't want to get pregnant, then I would suggest using another method.