Grab a paper business card and put it under your hand. Where the meaty part of your hand meets the wacom plastic. No more dragging from the friction between your hand and the board. It's very smooth. it's mostly useful for large strokes, btw.
A business card would drive me crazy since I remove my hand completely too often from the tablet.. I use, as some have mentioned above, woolen gloves with the fingertips cut off. Also keeps my hands warm when the AC at the office is being a sodding over-achiever..
talk about frustrating! do you know how long it took me to find a left-handed wacom tablet?! it looks the same as a regular one, but it cost me $100 more.