I was impressed today with Johanna Rothman's blog entry With Feedback, It's Kind to be Firm. I've always loved the bad-hygiene discussion problem. I completely agree with Johanna's honest and direct approach.
Let me add that this approach is not only most effective, it is also most respectful. While people don't enjoy getting these difficult messages, they will understand the respect you've shown them by being honest and direct. It is a deposit in what Stephen Covey calls the emotional bank account. This respect comes not from what you say, but from what they know you didn't say. By being direct, there is a natural perception that you are not gossiping about them behind their back. It is one thing to hear that you have bad breath; it is quite another to think people have been giggling about it behind your back.