Research published in the Journal of Clinical Endocrinology and Metabolism (is your subscription up to date?) even suggests that drinking water can actually help you lose weight! Something about water-induced thermogenesis:
In 14 healthy, normal-weight subjects (seven men and seven women), we assessed the effect of drinking 500 ml of water on energy expenditure and substrate oxidation rates by using whole-room indirect calorimetry. The effect of water drinking on adipose tissue metabolism was assessed with the microdialysis technique. Drinking 500 ml of water increased metabolic rate by 30%. The increase occurred within 10 min and reached a maximum after 30-40 min.
Of course, that's just one paper, and research published in the same journal earlier this month seems to contradict the findings.
Now, some people go overboard with the water. You've certainly heard the "rule" that you need to drink 8-10 glasses of water a day in order to maintain good health. Well, baloney. Snopes.com, the Urban Legends Reference Pages, debunks that myth. Furthermore, a Dartmouth Medical School study published in the American Journal of Physiology gives medical debunking to the "8x8" dogma -- eight glasses of water at eight ounces each:
the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
So, in addition to all my beverage consumption, I think the extra 500-750mL of water I'm consuming during the day is enough to keep me hummin'. My hourly (or more) bathroom trips seem to bear that out.