To read an e-book of any format on your computer or mobile device, you need to have specific reading software on it. Reading applications can be downloaded from the Internet for free. Please select software that is compatible with your operating system.

APPLICATIONS: PDF

PDF files can be read on any device with Adobe Reader or Adobe Digital Editions software. These applications can be downloaded for free at the Adobe web page:
Adobe Reader
Adobe Digital Editions

APPLICATIONS: ePub

Adobe Digital Editions is suitable for reading an e-book in Windows or Mac OS operating systems, but if you wish to read your e-book on an iPhone or iPod, please download Bookworm, Stanza or other compatible software.

Adobe Digital Editions
Operating systems: Windows, Mac OS
Formats: ePub and PDF
Other: Also reads DRM-protected text (DRM=digital rights management)

Aldiko
Operating systems: Android 
Formats: ePub 

FBReader
Operating systems: Desktop and a multitude of mobile devices and phones. Windows XP/Vista, Linux (also the following Linux based devices: Sharp Zaurus, Archos PMA430, Siemens Simpad, Nokia 770/N800/N810 Internet Tablet, PepperPad 3, Motorola A1200 and E680i/A780 smartphones, iRex iLiad
Formats: ePub, FB2, plucker, MOBI without DRM protection
Other: May change the layout of an e-book

Book Glutton: The Unbound Reader
Operating systems: web browsers (requires a connection to the Internet)
Formats: ePub (non-DRM ePub only)

Bookworm
Operating systems: web browsers (requires a connection to the Internet). Is also suitable for various mobile devices, including Apple's iPhone.
Formats: ePub

Calibre - eBook Management
Operating systems: Windows, Mac OS X, Linux
Formats: ePub (non-DRM ePub only)

iBooks
Operating systems: iPhone and iPad
Formats: ePub (non-DRM ePub only)

Mobipocket Reader Desktop (6.2 and later versions)
Operating systems: PalmOS, Windows Mobile, Symbian OS, Blackberry.
Formats: Mobipocket, ePub files are converted automatically to mobi format (non-DRM ePub only)

Stanza iPhone/iPod Touch
Operating systems: iPhone and iPod Touch
Formats: eReader, ePub without DRM protection

Stanza Desktop
Operating systems: Windows XP/Vista, Mac OS
Formats: Amazon Kindle without DRM protection, Mobipocket, Microsoft LIT, PalmDoc, Microsoft Word, Rich Text Format, HTML, PDF. ePub files can also be read on Stanza Desktop but the layout is inferior to that of other applications.

APPLICATIONS: MOBI/PRC

MOBI format can be read on Mobipocket Reader application. You may download it for example to Nokia mobile phones.

Mobipocket Reader
Operating systems: Windows and various mobile phones (see a list here).
Formats: .mobi

eREADERS

An eReader or e-book reader is a device designed specifically for reading e-books that is capable of storing hundreds of e-books simultaneously. Please note that Amazon Kindle does not support ePub files but does support Mobi and PDF files.

Different eReaders and the supported eBook formats:

Amazon Kindle 2, DX (PDF, Mobi, PRC)
Amazon Kindle 3 (PDF, Mobi, PRC)
Android Devices (PDF, ePub)
Apple iPad (PDF, ePub, Mobi)
Astak - eBook Readers (Available for North American market) (ePub)
Azbooka WISEreader (ePub, Mobi)
Barnes & Noble - nook (Available for U.S. market) (PDF, ePub)
BeBook - One, Mini (Available worldwide) (PDF, ePub, Mobi)
Bookeen - Cybook Opus, Cybook Gen3 (PDF, ePub, Mobi)
COOL-ER - Reader (PDF, ePub, Mobi)
Ectaco - jetBook (Available worldwide) (ePub)
Elonex - eBook (ePub)
Foxit eSlick (PDF, ePub)
Hanlin e-Reader V3 (PDF, ePub, Mobi)
Hanvon WISEreader (PDF, ePub)
iPad (ePUB)
iRex iLiad (PDF, ePub, Mobi)
iRiver - Story (Available for UK) (PDF, ePub)
Kobo eReader (PDF, ePub)
Nokia N900 (PDF, ePub, Mobi)
NUUT - Reader (Available for Europe) (PDF, ePub)
OLPC XO, Sugar (PDF, ePub)
Onyx Boox 60 (PDF, ePub, Mobi)
Pocketbook 301 Plus, 302, 360° (PDF, ePub, Mobi)
Sony - Reader PRS-505, PRS-900, PRS-600, Pocket Edition, PRS-700 (PDF, ePub)