We buy our tix at our local AAA. With any legit vendor (AAA, Undercover Tourist, Mapel Leaf Tickets, etc.) you will at most save about 5%. It may make more sense to buy them direct form WDW when you arrive if you consider the value of keeping your money in the bank for a few extra months. We sometimes do buy them our first night at Downtown Disney.
We have purchased our WDW tickets from http://discountorlandovacation.com/
and have been very happy. They have outstanding prices. There has been a thread on this board in the Sea World forum about getting Seaworld tickets when you donate to the NRA: http://www.disboards.com/showthread.php?t=1515410
While I am not a fan of donating to the NRA, I did get 6 tickets for Seaworld for only $150 which is less than half the price from any broker. I got the tickets within a week of making the donation. The tickets can be used at either Seaworld or Busch Gardens. Check it out.
I agree with undercover tourist. If you have time before your trip, sign up for the Mousesavers newsletter (it will be sent to you on the 15th of each month) and she has links to discounts exclusive to her readers through them. The prices may look similar to those on Disney's web site but they include taxes and shipping.
If you can get the price mentioned above for Sea World by donating to the NRA, you may want to do that. It cost quite a bit more for us to go there this past February.
Universal has a great deal on line for $86/person for up to seven consecutive days of admission.
We used the Official Ticket Center. They have an ad in the bottom of the ticket section of the Dis. The price was about $2 more then AAA, but if you bought a 4 day pass, they gave you an extra day for free. They were kind enough to charge us the price of a three day pass and they threw in the extra 2 days for free.
Another big thumbs-up here for Undercover Tourist! I was pleased not only with the prices but also the service. I do realize that $210 is the quoted price from WDW for a 7-day ticket, but that is before taxes. UT had $203 for a "5 day ticket plus 2 free days" - OK, but that included tax and free shipping. Worked for me. And I ordered them last Thursday night and received them at my office (in New Jersey) on Monday!!!
Edited to add: for 2 adult and 1 child ticket, we paid $598 total.