I talked to alot of people about this last week (CNC 2005 over 400 miles through NC).

Everyone had their own opinion, it comes down to trying which works best for you.

Personally, I used Udderly Smooth Udder Cream (from walmart, about 98 cents). I applied it liberally to my skin and chamy. Even on the days that it rained all day and I rode 82 and 65 miles in the rain, it held up.