The Pragmatic Studio (http://pragmaticstudio.com/) has released six free screencasts to help developers transition from Xcode 3 to Xcode 4 and learn new time-saving keyboard shortcuts.
This initial round of screencasts is geared toward developers familiar with Xcode 3 who want to make the jump over to Xcode 4. Many of the concepts will be familiar to iOS developers, but the screencasts will help guide you around the new user interface. There is also a handy Xcode 4 Shortcuts Cheat Sheet available for download.
In their upcoming hands-on iPhone/iPad Programming courses the Pragmatic Studio will be teaching Xcode 4. It will be held April 18-21 in Denver, Colorado, and July 18-21 in Reston, Virginia.