I'd highly recommend Loyalty Homes www.loyaltyusa.com It is a company based a few miles from Disney which is owned and managed by an english lady called Yvonne. The management company has been running for over 10 years now and she only manages luxury homes with pools (many also have gamesrooms) which are less than 4 miles to Disney. She has managed my home for 10 years and I'm very happy with her service and am happy to recommend her.
We advertise our Emerald Island villa on The Dibb. Unlike most websites they insist on seeing proof of ownership before allowing people to advertise villas on their site so they're probably more reliable than most.
We also recommend The Dibb as a source of information and accommodation. Our Aviana villa is also advertised and as The Dibb is an open forum and the Dibb Villa owners all strive to provide exceptional one to one contact, unlike dealing with a tour operator.