Create Your Own Cloud of Ebooks with Calibre + Calibre OPDS + Dropbox | http://dearauthor.com/ebooks/create-your-own-cloud-of-ebooks-with-calibre-calibre-opds-dropbox/
This post has been updated as of October 16, 2011. Apple appears to have pushed Google out of the ebookstore. Kobo released an updated app with no buy link. Google is randomly deleting Google Plus accounts. Yet another ebook format has been announced.