Like Chopper mentioned, getting a dispatcher licence is not cheap (with travel expenses, hotel bills, course fees it'll be approx 10,000USD), but if you can organise the funds required I recommend Flight Safety LaGuardia NY. Most of their instructors are part timers who have full time jobs with airlines in dispatch and related fields. The result is that you get to learn the theory required for the exam, but also get a more practical background on how to put all this knowledge to use in a job situation. I go there for annual recurrent training and I learn something new every visit. Email their head instructor Sabry for course dates and prices.
[email protected]. If you do book a course, stay out in Garden City Long Island near the Roosevelt Mall. Downtown Manhattan hotels are severely over-priced at the moment.