Update: Acquia has released a great migration whitepaper to help you get ready to move to Drupal.
My position with Acquia will find me helping out with a lot of migrations and upgrades. I'm going to embark on a multiple-part blog to discuss some of the common techniques that I use when moving clients to Drupal.
Migrating to Drupal can seem intimidating if you already maintain a database-driven website. However, populating a Drupal site with your current content might be easier than you think. Whether you are migrating from a popular CMS or a fully custom application, you can easily use Drupal modules to mimic your current data structures and migrate your data using a simple custom PHP script. I should note that while there are several different methods to accomplish this task, this happens to be my favorite.