Into The Oven!!! www.intotheoven.com Cheaper for me than my local cake decorating shop, even with shipping, which by the way is always fast and on time (for me it's three days).
I've never ordered from them but the prices look good:
www.****************** (without the spaces)
I've never ordered from them but the prices look good:
www.****************** (without the spaces)
coupon code "cakecentral" will save you another 10% here 
If you join the Into The Oven forums, you will get periodic coupon codes (I just got one about an upcoming SI sale) and they also mention specials in the forums. There is a link from their homepage.
Global Sugar Art when it is on sale (which it is now) and Pfeil and Holing - best prices, great shipping.
cookiesup: I ordered a cake pan and some bags from cakesbysam.com just last week- great prices and fast shipping!
Edited to add: I've ordered fondant from www.****************** before. They also have good prices and shipping. I also like Global Sugar Art and Into the oven (though I've never ordered fondant from intotheoven.com). I've had pleasant ordering experiences with all three. 
Edited again: Oh! Now I get the "spaces". That was supposed to be the url to fondant <space> source. 
Quote by @%username% on %date%
%body%