A fanlisting is simply an online list of fans of a subject (in this case for .hack//all series) that is created by an individual and open for fans from around the world to join.
There are no costs, and the only requirements to join a fanlisting are your name and country. Fanlistings do not have to be large sites (although some are), they are just a place where you can sign up with other fans. TheFanlistings.org is the original (but not official) web directory for fanlistings, dedicated to uniting the fans.
Description from tfl.

.hack is a big commercial project produced by the well-known company BANDAI with the support of CyberConnect2. It comprehends not only the 4 MMORPG (Multiplayer Online RPG, or well a role playing game only playable on-line), which actually simulate this kind of web-games, but also 2 OAV series, one TV serie, manga, novels and card games. The world of .hack knows different stories, and different main characters, although every "piece" of this experience is linked togheter, as a puzzle. But let's analize the animated products! I'm not trying to make a complete review, but only to introduce the "newbies" to .hack...so consider this page a spoiler-free summary!

This serie of 4 OAV is sold togheter with the video-games, each chapter is actualy related to each release. This product is really original since the story follows the happenings outside "The World" (the virtual reality, setting of the main story), and it's about the events concerning the real world. As for the games, in each OAV the main character is different as well as the particular plot of her side-story (except for the last one, which regroups all those protagonists!).
I really reccomend liminality if you want to add more "knowledge" to your .hack experience!

Peraphs the most famous of the .hack related products, SIGN is the anime tv serie. In Japan, and as well abroad, it got a really significant success, mainly because of the great quality of the product itself and also because of those "huge" names involved in its development, like: Kouichi Mashimo (direction; Noir, Irresponsible Captain Tylor), Kazunori Ito (screen-play; Ghost in the Shell, Patlabor) and Yoshiyuki Sadamoto (character design; Evangelion, Wings of Honneamise).
The story is set 6 months before the events of the games (so in the year 2009) and the main character is Tsukasa, a player who gets in touch with The World by chance.
But once he enters in the World he can't live it and come back to his reality, remaining entrapped in that virtual dimension. So he'll begin to wondering through the World, moving from one "layer" to an other, looking for "The Key of Twilight", the mean tht could bring him back to his world.
.hack//SIGN is composed by 26 episodes in which not only Tsukasa, but as well all the main characters, are really well developed and analyzed, in all the aspects of their personality. In watching this beautiful anime you can live their virtual, but yet "real" adventure.
The OST of this anime is a must have, since all the tracks are original and they fits each moment of the animation. Above all the two themes are lovely (Obsession, the opening and Yasashii Yoake, the ending), both sung by the rock group See-saw (who have also composed the themes of the OAV).

Based mainly on the manga, DUSK or Legend of the Twinlight is set 4 years after .hack//SIGN and the videogames. The CC (the company producer of the online game), a "Limited Edition Character" campaign for The World players and participants, in which the prize consists of the avatars of thos legendary characters (Kite and Black Rose) who were responsible of the "Twilight Incident". Rena and Shuugo are the winners of the contest and they begin to play the game enjoying themselves and meeting up with some other characters. But the World isn't as peaceful as they expected and it seems the accident that happened in the past brought much more consequences than expected...

Coming soon!