American Medical College Application Service
AMCAS is a centralized application service for people applying to medical school. It is used by most medical school programs. This helps you submit one application that will go to multiple schools. You will then likely receive supplemental application materials from schools you apply to.
Information and application deadlines can be found here:
One major exception of schools that do not use AMCAS are several Texas medical schools. These schools use the Texas Medical and Dental Schools Application Service (TMDSAS) (Most of these schools, however, use AMCAS if you are applying for a MD/PhD program.)
Application deadlines are set by individual medical schools for regular applications. The exception is applications for the early decision program are due for all schools by August 1st.