All available CTP courses can be found at www.faa.gov/pilots/training/atp/media/atp_ctp_providers.pdf. Note that some of those providers are in-house courses for regional airlines.
Hands down the best CTP provider is the Delta Training Center. It is a unique opportunity to complete the FAA CTP requirement while taking advantage of incredible networking and training (747, 757, 767, 777 sims) opportunities. We have heard nothing but positive feedback from our students. Sign up for the CTP (or the entire Mil-to-Airlines Course!) on our website.
For the written, Sheppard Air is the simplest way to go. Two weeks of studying and $75, and you’ll be ready for the test. www.sheppardair.com/atp.htm
For the ATP, of course we recommend our program! Whoever you choose, we recommend finding a military friendly school to provide you training suited to your flying history.