Today we have the top 3 web-sites to read manga online :

1.Manga Fox

Their is an amazing collection of manga in Manga Fox.

2.One Manga 

it also has an amazing colletion of manga ,but Manga Fox looks better than One Manga  so it's the second place to find your manga .

3.Mangareader

This website allows you to read thousands of manga online. Besides reading online, you can also download them.