There is much more to online TG fiction than Fictionmania, although that site is by far the largest.
There are definitely other story collections out there that are worth exploring (and which will also help you get your daily TG fix when Fictionmania is slow and unapproachable).
Sapphire has collected TG stories for years from all over the Web and presents them over at Sapphire's Place.
Do not let the rather bland design fool you. Much of the content is hot, so hot if fact that Sapphire even uses a fire logo to label especially interesting stories.
That's a good thing, as this site - like all other TG sites - is pretty hard to navigate. You have to go through a lot of content to find the gems, as there are no tags or topic categories.
It gets easier as soon as you have identified favorite authors, though, as there is a separate author's index. There is also an episode guide to serials.
The message board is down, but if you are writing TG stories yourself you should consider signing up for The TG_Fiction Mailing List.
The participants are very good at keeping each other informed about new stories and online TG related stuff. You may also get help with your own stories.
By the way, there is more than textual content here. You will for instance find an overview over Bikast's computer animated TG videos.
The illustration is from Big Naturals.