Some Drupal links for developers
Some good Drupal developer guides or reference pages
Forms API
CCK
- Some info about CCK widgets http://drupal.org/node/823858
- CCK widget http://poplarware.com/articles/cck_field_module
Views
- Views online help http://views-help.doc.logrus.com/admin/advanced_help/views
Theme
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About overriding themable output http://drupal.org/node/173880