- Google Plus API & photos? - Stack Overflow - use Picasa Web Album URL
- image - Google Plus Album Urls - Stack Overflow - all Google+ Photos are Picasa photos. You can get albums back as JSON too
The Google Drive integration, by the way, is a dangerous hack. Avoid it for now.
The Picasa uploader doesn't support Google Photo's image compression format (WebP?), so I wonder if those images will count against storage totals.
I hope we get an API, particularly with support for creating or selecting albums at upload time, any minute now...