Yep - just sent a box with 21 or 22 canisters from Seattle to Virginia. It was a huge pain in the rear trying to get someone to give me a straight answer. In the end, I had to get a document from Coleman (they were Powermax canisters) - which fortunately is on the web - and give UPS a transportation code for the specific fuel canisters. My local USPS just flat out said they wouldn't ship them. My guess is they weren't clear on the regs and didn't want to deal with hunting them down.
Once I had the data sheet on the fuel, I talked to a specialist on the phone who walked me through how to label and ship. The UPS counter person had told me they don't know how to do it and I need to talk to a specialist. In the end, it was actually pretty straightforward. Canisters have to be under a certain size (pretty much all backpacking fuel canisters are) and label them with a specific diamond-shaped label. Cost was the same as anything for that size and weight, so no extra fees.
I have the diamond label image UPS sent me as an attachment. If anyone wants it just send me a PM with your email address and I'll forward it along.