Here are some good ways to keep female desire high:
1. Read romance novels with steamy sex scenes.
2. Look at erotic art or a sexually-themed blog (http://theracerx.wordpress.com/ is all about sex, and includes erotic art).
3. Run erotic fantasies through your mind when you are away from your husband and have a few minutes to do so.
4. Buy lingerie for use during sex - and wear it! It can be impractical and scratchy; it just needs to look good and make you feel like a sex kitten. You won't have it on long anyway.
5. Buy lingerie that is comfortable enough to wear to bed. I personally like the slips sold at Victoria's Secret. Wear one of these even when you are not trying to get laid. The idea is to feel sexier in general.
6. If your husband is not available for sex when you feel horny, take care of yourself. If your desire is ignored, it will lessen. You have to feed your sex drive for it grow.
7. Most importantly, never say no when your husband wants sex. (Unless you are ill or absolutely exhausted.) All those wonderful chemicals that happen in your brain during sex bond you to your husband and make you want to have sex with him more.
In short, think sexy thoughts, look at sexy stuff, and have lots of sexy time. Sounds simple to me. And quite enjoyable too!