[Update: Photoshop product manager John Nack has more info and references in CS5 is Alive!, and later Dave Howe adds more Links to CS5 Coverage. See also Fxguide's Photoshop CS5 : New HDR imaging & Content Aware Functions.]
Adobe TV's Photoshop CS5 Feature Tour is already heavy with intro movies and includes Russell Brown's Top 5 Photoshop CS5 Features.
Lynda.com is filling out its intros; see Adobe Creative Suite 5 new features training previews. Here's Chris Meyer on Repoussé in Photoshop CS5 for AE:
NAPP’s Photoshop CS5 Learning Center also hits the ground running.
Some of the features of Photoshop CS5 are available in the free open source app GIMP. Content-Aware Scale is called Liquid Rescale in GIMP , while Content-Aware Fill is called ReSynthesizer in Gimp. For a few details on these implementations, see More free Photoshop with Content-Aware Scale with the GIMP at Blender 3D Architect. Even with GIMPshop to reorganize menus, GIMP would take some getting used to.