In my post We're all Junkies I ask the reader to go to Google and find the evidence for why sugar is bad.
I did some digging myself this morning, and found a couple of sites which appear to be reliable sources.
On Sugar Addiction: Society for Neuroscience [link removed] - this seems to be an organisation with a good reputation. Update, 3rd Oct 2010: this link was removed because it no longer works - however, this article summarises the content of the paper that was published in 2003.
On the damage sugar does: Mercola.com - whilst Dr Mercola is selling products, the references he gives in this article are from respected medical journals. Note that one or two of the articles he cites refer to the consumption of high concentrations of simple sugars, not specifically refined sugar.
We’re all Junkies
Cigarettes, Sugar and our Innate Short-Termism
The Worst Sugar Pushers of all - Health Food Stores