I don't think there's any place you can get tickets for a "great" discount. Most of the discount places are selling them for approximately the same prices as each other. AAA is $1 cheaper than buying them in advance from Disney!!! But overall, you will save some money buying in advance rather than waiting til you get to wdw, regardless of what discount ticketer you use or if you use Disney.
2 tips:
--if you are looking for a 3 day plus hopper, call Alamo rent-a-car's 1-800 number... it'll save you money when compared to buying a 4 day hopper (most discount ticketers sell 4 day hoppers as their lowest amt of days; the 3 day is very hard to find)
--don't be fooled by the price quotes at the disney website! They are listing prices without taxes!! For example, a 4 day hopper is listed at $192 but once you add it to your shopping cart, they add about $12 tax!