For all disney related discount and money saving info:
www.mousesavers.com
For general info on anything you could possibly want to know about Disney (they also have forum areas for Universal and Sea World):
www.disboards.com
If you find what looks like a great deal that you can only get from one particular travel agency, it's probably NOT a great deal. Disney is very particular on what kind of discounts they allow and all of them will be available by booking directly through Disney. Mousesavers is the best source of all legitimate discounts that are available.
Disney sometimes offers discount codes that only apply to packages, but otherwise, booking a package will NOT be cheaper than booking your room and buying your tickets separately.
You will NEVER find a huge discount on Disney tickets. If you do, there's a 100% likelihood that it's a scam. But there are a couple of authorized resellers that always sell tickets for a slight discount (usually 5% or less off). You can check them out via Mousesavers.
As far as booking a room at a Disney resort, there are a couple of different discounts that are often available.
AAA - You can save 10-20% off the rack room rate if you are a AAA member. This discount is almost always available (Easter and Christmas may be exceptions). And you can book it directly through Disney by asking for the AAA rate. You will be asked for your AAA card when you check in.
FL Resident - If you are a Florida resident, there are sometimes discount codes available. These are usually available a few months in advance. Check Mousesavers.
Annual Passholder - Typically similar to the FL resident rates, but for Annual Passholders.
General Public - similar to above, but these discount codes, when available, can be used by anyone. Again, check Mousesavers for any current deals.
I'm less familiar with Universal and Sea World, but I can probably answer pretty much ANY question you have about Disney World.