It is hard to tell which sellers are legit. Disney, Disney stores,
AAA, and Undercover Tourists are ones that I have used. I am too nervous to use anyone else besides these guys. They also sell Disney tickets at Wal Mart down in Kissimmee and Davenport. I don't think you save much, but it might be easier than waiting until you get to the parks to buy them. If you sign up for the mousesavers newsletter though
www.mousesavers.com, you will get a special link (on the 15th of each month) for discounted tickets through
Undercover Tourist. The prices though the special link that is sent to you, include taxes and shipping which makes them a pretty good deal. I have also heard Maple Leaf tickets are reputable, but I have not used them. Whenever you get your tickets, it is always a good idea to photocopy the back of them. If something happens that you lose a ticket for some reason, guest services can reissue you tickets if you have this information.