I refer most folks looking for a deal on Speedhubs to eBay. They pop up with regularity, although of late thier prices have been creeping upward. But set up a "favorites" search for "(Rohloff, Speedhub)" and their system will generate an email every day if a new one is put up for bids.

HarrisCyclery.com is big on Speedhubs. I believe WebCyclery.com stocks them. They're listed in the QBP catalog, making them available on a ton of "cookie cutter" LBS websites, plus places like aebike.com and bikeman.com. There is also a Canadian website called FreerideHubs.com that appeared to have centered their business around the Speedhub before having a fallout with Rohloff, which is the main subject of their website of late.