Entry to the Club will cost you $24.99, and will net you an exclusive theme as well as access to the first four multiplayer map packs and the first three multiplayer skin packs for Uncharted 3: Drake's Deception. Sony values the DLC at more than $45 when purchased separately, so there's a definite saving on offer.
You'll also be reminded each time a new piece of DLC launches, with an XMB message from the Fortune Hunters' Club directing you to each download when it becomes available. The first pack is due out in November, and new releases will follow from there on.
Head over to the PlayStation Blog for more details.