Out of the board sponsors, TGB probably has the best regular prices when factoring in the coupon codes floating around. TFSupplements is a close second. There are also several sites that I cannot mention tht have some good deals on X-Gels right now.
In terms of sales, Nutraplanet 9 times out of 10 has the best prices on sales. These sales are around holidays. Next one will probably be Memorial Day, which is a good thing since I need more money for the pending sale!
Also, sign up for supplement companies newsletters. They usually have good deals on new products or even just out of the blue.