ANIP
A barebones site as far as presentation, scroll down and you will see ANIP (http://anip.homeunix.com) provides tons and tons of manga titles.
Some of these titles you can view online right in your browser however this is a minority of the manga titles compared to the whole list. To see these manga issues, click Read Manga on the menu.
Many of the titles needed to be downloaded to view. They are torrents, so you need a torrent program like BitTorrent to download.
This site looks relatively new. I didn’t not find a lot of older issues, which is fine for me and most people anyway.
The nice thing about this site is these guys have put a lot of work into making sure you can get the manga (multiple servers, decent download times) and they provide it completely free–they ask you send donations to the scanlators–because they love it. You gotta love guys like that.