Here is a chronological list of all the Republican and Democratic presidential primaries, caucuses, and conventions in 2012.
There are data to the states' rules. For instance:
Tuesday 24 April 2012 (tentative): 81 of 95 of New York's delegates to the Republican National Convention (3? from each of the state's 28 Congressional Districts) are allocated to presidential contenders in today's New York Presidential Primary.
There are also links to state constitutions, election authority (e.g. state Board of Elections), legislature, political parties and media.