Paul Thurrott, co-author of Windows Vista Secrets and Windows 7 Secrets, is working on a new book named Windows Phone Secrets. He published a lot of Windows Phone 7 screenshots from the unlocked version of the Windows Phone 7 emulator that came with the most recent developer tools.
The collection includes screenshots of phone (voice) screens, calendar, media main screens (photos, music, radio, Microsoft Office components, SharePoint, maps, ringtones, and system menus. All the screenshots are in portrait mode. I wonder if the sliding view design might cause problems for people who prefer to work in landscape viewing mode.