Depends on the resort, and what you mean by 'facilities'.

At the WDW DVC resorts, recreational activities like boat rentals are available to the public. You can dine or shop at a resort without being a guest there.
Resort pools are going to be off-limits anywhere. The pool-hopping specifics can be found on the DVC member site, but at WDW, you need to be a registered guest at a DVC resort to be able to pool-hop, and not all pools are open to you.
Check out our DVC Resorts board for the details on Vero and Hilton Head. Aulani has its own board.