Free eBook Reader Apps
Kindle
Devices: iPhone, iPad, Android, BlackBerry, Windows PC, Mac, and Windows 7 phone
Registration required: Yes
Advantages: Large store, a few contemporary books temporarily free, integration across devices (sync, bookmarks, etc), free samples, search inside a book, ability to read certain newspapers and magazines, Night mode
Kindle Apps
Nook
Devices: iPhone, iPad, Android, PC, Mac, and BlackBerry
Registration required: Yes
Advantages: Relatively large store, a few contemporary books temporarily free, integration across devices, free samples, ability to lend books, search inside book
Nook Apps
Kobo Reader
Devices: iPhone, BlackBerry, Android, Palm Pre, BlackBerry PlayBook, Android Tablets, and PC Desktop.
Registration required: Yes
Advantages: store, a few contemporary books temporarily free, integration across devices
Kobo Apps
iBooks
Devices: iPhone, iPad
Formats: ePub and PDF
Registration required: Yes
Advantages: store can be accessed through iBooks or in iTunes, Integrates well with iOS, small collection of free books, free samples, integration across devices, print PDF documents
Stanza
Devices: iPhone, iPad
Formats: ePub, DjVu, CBR, CBZ, PDF
Advantages: Night Mode, easily download books from both paid and free sources including Project Gutenberg and Smashwords
Registration required: No
Stanza
Bluefire Reader
Formats: ePub and PDF
Registration required: No
Advantages: Night mode, ability to read files protected by Adobe Content Server encryption technology (including library ebooks through Overdrive).
Bluefire Reader apps are available for the iPhone and iPad.
Bluefire Support
Knot of Light is focused on apps, ebooks, music, iPhone wallpapers, and other resources that relate to mobile devices. Updates vary depending on the available news.