Yes, all of the onsite resorts have broadband service. Cost is $9.95 per 24 hour period. There should be an ethernet cable in the room (usually hanging in the closet) - but if it's not there, just call and they will bring one to you.
Some of the resorts also have wireless access in public areas (also for a fee) amd all resorts have dataports for dialup ($0.35 for DVC members staying at DVC resorts and $0.75 for other guests). There is no WiFi available in the villa rooms though.