MangaDex - MangaDex is an online manga reader that caters to all languages.
Mihon - Free and open source manga reader for Android
MyReadingManga - Myreadingmanga is a community-driven platform where you can find comic books of any type.
Houdoku - Manga reader and library manager for the desktop
Manga Effect - Manga Reading, manhwa and manhua online, the fastest updates. Mangaeffect is a colour Manga Read in English for free. Daily Updates!
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.