There are other discount/third party ticket sellers that get mentioned here on the Disneyland Disboard: GetAwayToday, aRes, way.com, Expedia, Orbitz,
AAA, and Costco (ocassionally). There is also
CityPass, which lumps together multiple attractions in Southern California.
I looked into Undercover Tourists a few months ago and they did not sell Disneyland tickets. They only sell tickets for one of the bus services that go from the airport to DLR (not run by Disney).