Thanks, Jill! I just copy/pasted from the thread below.
Here's the start of known reputable online and bricks & mortar shops. I set these up as direct links to their main pages with the exception of Overstock. I set that link up to take you directly to the Prada handbags. And please don't try linking like this at home! I'm cross-eyed.
These are the first that came to mind, but I know there are tons of other smaller, reputable sites out there, I'm just drawing a blank right now. If anyone thinks of one, drop me a PM and I'll set it up as a direct link.
With the exception of Prada Authorized Retailers (such as Neiman Marcus, Saks, Bergdorf Goodman, etc.), always get your items authenticated. The secondary market, even the most reputable of resellers, have been flooded by Super Fakes.