Long-rumored, but finally true. Adobe has announced a public beta program for Photoshop CS3. While the finished program is not yet ready for release until the Spring, it is almost ready for 'prime-time.' You can read more about the release on Adobe's website for the full details.
If you are looking for some training, here's two places to start:
Photoshop CS3 Sneak Peek – On the Web – On iTunes
Photoshop CS3 Learning Center – On the Web