The best program going right now, at least in my opinion, is at LECOM Erie...I'm currently enrolled BTW.
You have to have already completed the medical school prereqs (1 yr of Bio, Gen Chem, Org Chem, Phys).
The program starts in Sept. and is 8 months long. It's NOT an academic enhancement program. You take the same classes that a 1st year and 2nd year would take, with the same professors and powerpoints, but in 2 semesters instead of 2 years.
The program is difficult...but definitely doable. The requirements for direct admission to the medical school are that you get a 3.0 in the postbac and get (within 3 years prior to admission) a 22 on the MCAT. The website incorrectly notes that these stats only get you an interview...the reality is that a 3.0 and a 22 get you automatic acceptance to the DO program.
Apply early, visit the school, and get the booklist. Study Physio and Biochem before you arrive and you'll do just fine in the program.