There are approved places where you can save a few dollars, and depending on how many tickets you buy and how many days you want it might be worth it. An approved seller will have something that says they are approved by Disney, they will have Disney signage. Most of the places referred to in the post above will happily show you documentation. My basic rule is to stay away from any place with a big balloon outside and signs that say CHEAP TKTS HERE!!!
As a former ticket person, I beg of you PLEASE make sure that your ticket discounter is approved before you hand over that credit card. There is nothing worse than getting to the turnstiles and finding out those "discounted" tickets were used by someone else and you can't get into the park. And I know someone has a story about his sister's/cousin's/brother's son in law who got in after being scammed-but Disney's sympathy for such things has pretty much run out. (same with Universal, so I understand) I've seen families have to fork out the money for the real tickets and pretty much know that they would not get their money back from the balloon place they bought the tickets from. Unless you go with a cop, they're just going to laugh you right out of there. Nobody wants to buy tickets twice.
Also, approved discounts are offered through time share presentations-but as Pete said on a recent podcast-know what you are getting into. It's a LONG presentation, will take up most of your day and it will be very high pressure.