You can also try penana.com. It's rather new but I guess it means you have higher chance to get noticed! Though it doesn't have a mobile version of the site yet.
Fanfiction.Net, Mibba, Tumblr, AO3 (Archive of Our Own), Ficwad, Fictionesque, Mediaminer.org, AdultFanFiction.Org, GaiaOnline (You have to look through the writing section of the forums there since GaiaOnline is one big social site and it's a big clusterfuck of teens on there so you'll have sort through the immaturely written stories to find the real gems there), there's RockFic.com if you like bandfiction, and that's all I can think of.
Quotev. It really depends on the fanfics on there though. Most of the writers and readers are teenagers, so it's not written the best. There are some really good stories if you search enough.
Wattpad and Fanfiction are the only others I know of. I never used wattpad and only read on fanfiction.net.