Chaos Tool Suite is one of the best API module to use. The module mainly provides API. I've worked on ctools before to create multi-step form and show that in popup. This time I'm working on a project which has a Quiz in it which is built using ctools.
Views one of the great module available in Drupal. Views can be used to show various types of dynamic data and can also be used to allow users to filter results based on his criteria.