The Presidential Nomination Process

Helena asked about the history of the unit rule in the electoral college. A brief (albeit opinionated) summary is here.

Madeleine asked about the complex system of federal matching funds. You may find more detail here.

The New York Times has good information on the delegate-selection process, including the latest dates for party primaries and caucuses. Before any official delegate selection there are unofficial events such as the Ames straw poll.

If you want to see some brief clips of Iowa caucuses, see here.

And the Dean Scream ... from a different perspective.