Mihon - Free and open source manga reader for Android
MangaDex - MangaDex is an online manga reader that caters to all languages.
Miru Project - A versatile application that is free, open-source, and supports extension sources for videos, comics, and novels, available on Android, Windows, and Web platforms.
Manga Fox - Read your favorite manga online! Hundreds of high-quality free manga for you, with a list being updated daily. Naruto manga, Bleach manga, One Piece manga, Air Gear manga, Claymore manga, Fairy Tail manga, Inuyasha manga, and many more...
Houdoku - Manga reader and library manager for the desktop
Mangainn - Read absolutely free and daily updated hundreds of high-quality manga online