I am very prone to the Yeasty Beasty, as well. For me, the vaginal yeast is always somewhat related to intestinal yeast overload and I'm just an itchy gassy mess at that point. What works for me:

1. Cut out the refined sugar and processed carbs for a while. Really, it's best for me to avoid the stuff in general, but I always end up eating more than I should. Some of the worst yeast infections (and UTIs, for that matter) have happened during the holidays with all of the candy and desserts and starchy foods. The only times I can get away with eating a lot of refined carbs is before, during, or immediately after an intense ride. It can also help to avoid fermented and pickled foods, as well.

2. Keep my intestines happy by making sure I consume a lot of good friendly flora. If I'm really yeasty I'll also take a supplement called caprylic acid which is a natural antifungal. No matter how careful you are with hygiene, the bottom line is that if your body's conditions favor yeast in one department, it will be favored in the other department as well.

3. Topical treatments: acidic rinses/douches with vinegar or lemon juice, topical application of live cultures such as plain unsweetened yogurt or buttermilk, etc. Boric acid capsules and garlic cloves for really full-blown cases. All good stuff. I often use an OTC anti-yeast cream as my chamois cream anytime that I'm cycling and feeling borderline itchy.

3. No soap, bodywash, etc. Period. The vagina is made of mucous membranes very similar to those that line your mouth and eyes. Would you wash your mouth or eyes out with soap?

4. Vaginal pH management - this is the most important part. A happy vagina should be nice and acidic (~3.5-4.5 pH) to discourage yeast and bad bacteria and to encourage good flora like acidophilus (acid loving). Some common alkaline invaders are soap (see previous) and semen. That's right, the ol' demon seed is an alkaline material designed to counteract the acidic environment in the vagina so that the little swimmers can penetrate our fortress. If you frequently come into direct contact with this material, it's a good idea to swish the stuff out with plain water or a slightly acidic solution postcoitus. If you do use a barrier method with spermicide, you might want to flush that out too as it can kill your friendly flora too.

BTW, your pH is more alkaline in the week before your period, which is why it is more common to have yeast infections right before or during your menses. It also changes during pregnancy which can lead to more frequent yeast infections to add to the discomfort.