AlternateHistory.com is currently the internet's largest Alternate Historysite since the collapse of Soc.history.what-if. Revolves around a discussion forum that has been in existence since 2000 and in its current form since 2004. Has produced a great deal of AH fiction output; a full list of timelines with links can be found here on the site's wiki.AH.com has also produced some AH, science fiction and fantasy stories in the form of prose, which can be found here.However, the forum's Off Topic section is also notable for having developed its own subculture over the years, filled with Running Gags and Memetic Mutation. All of this has found its expression in AH.com: The Series, a satirical comedy-cum-drama (Depending on the Writer) series parodying both common Alternate History settings and tropes, and more generically the futuristic sci-fi setting of the titular crosstime ship. The crew and most of the guest cast is made up of fictionalized forms of the Board's own members. If it can be categorized as a Self-Insert Fic, we can only conclude that most AH.commers are raving sadomasochists, given what usually happens to the crew.In addition to the main Series, there have been several other similar productions, such as Luaky Commer and AH.com Wars (parodies of Harry Potter and Star Wars starring the characters from the Series), the Spin-OffAH Dot Com The Next Generation, and others.As a disclaimer, however, much of the content, including the Future History, ASB and Off Topic sections, on the forum is accessible only to logged in members. The main logic behind it (according to the moderators) is so that it would encourage people to sign up for the more "serious" discussion threads, with the rest available afterwards (with a Writers' Block section sensibly restricted for copyright reasons).It also has a Shared Worlds section divided up into Shared Worlds, Moderated Games, Nation Games, and Map Games.In addition to their main wiki, they have also created their own variation on TV Tropes, titled (of course) AH Tropes. It's currently in its infancy, so Wiki Magic is necessary.
Argentina Is Naziland: Averted. The board has long deemed this an overblown cliché, whether in AH works or real life (the idea of Nazi emigrees setting up a Fourth Reich in South America is ridiculed in particular).
The entire forum has a (memetic) tendency to get riled when people start talking about Operation Sealion (Hitler's plan to invade Britain) because discussion has long since been played out and there is a universal consensus that the plan was so badly conceived that its success was essentially impossible.
Eagleland: When "Ameriwank" scenarios come up, generally their authors have flavour #1 in mind and everyone else is pointedly reminded of flavour #2.
El Spanish O: A Running Gag on the site, started by member Thermopylae, who refers to map updates to his timelines as "El Mappo!", and later used by the Heterosexual Reconquista.
Everything's Better with Plushies: Several years ago, the site started the "Sealion World Tour". This joke project is still on-going in 2011. The members send a plush sealion named Sealion from one member to another, who'll take pictures and post them on the forum. Sealion has been to four continents so far and has last been seen in Brazil. The reason they used a sealion ? It's an ironic mascot of the site, referencing a surprisingly popular yet horribly implausible AH scenario. Read the Berserk Button entry above.
It gets better when you find out the person who is supposed to receive said stuffed animal in the end is nicknamed on the forum..."The Overlord".
Different World, Different Movies: Naturally, alternate popculture is a frequent feature of many of the board's AH stories and projects. Pages compiling some discussions on these topics can be found here and here.
The board has grown tired and irritated of most of Harry Turtledove's newer AH novels.
S. M. Stirling was once a member of the board, but revealed himself to be quite a jerk and got banned for it. Opinion of him has mostly lowered throughout the board since then (in addition to most people being critical of some of his AH works to begin with).
Did you know that atom bombs are a hoax perpetrated by Jewish tribalist uncles who sit inside nuclear reactors rubbing vaseline into potatoes ? Apparently, one (in)famous banned troll virulently believed in this. It became a minor meme on the site after his banning.
Other bits of famous AH.com troll logic include the idea that graffiting on pavements will cause gay couples to jump off bridges, and something to do with public trees on private land (or possibly private trees on public land). See here for more details.
Network Decay: Periodically people will rant about the decline of the "History" Channel and other documentary channels that are supposed to focus on history.
No Name Given: The Sealion World Tour (see above) featured a stuffed toy sealion called... Sealion, because nobody could think of a suitable name. He was eventually dubbed "Silas" by the Brazilians, a Punny Name that only works in Portuguese.
The aforementioned collection of silly names for a "Eeebiiiil MuslimMiddle Eastern Coalition". A variant is the "Boat People's Caliphate", a mocking name for a hypothetical Indonesia-led alliance of south Asian Muslim countries (a staple of the already cliché scenario "random near future war between Indonesia and Australia").
Another notable running gag is that all the German members on the forum actually constitute a Hive Mind - despite their constant political arguments, which are held to be only an elaborate cover.
The Universal Colour Scheme (UCS), and by extension, map colour schemes for alternate history maps in general. Resulting in a feud over a proposed revision to UCS. The Change: Moving Non-Communist Russia from a Gold-tone to a Green, but then, it was Decided By One Vote (well, two votes - 183 to 181), so obviously lots of people argued.
The more recent "PonyWars" ended after several members were banned, several more had their posting privileges temporarily revoked, and a moderator being demoted. People still are hesitant to discuss it today.
Shown Their Work : Because of their love for the genre, the members of the board try to do this as much as possible - even when writing deliberately silly and Rule of Fun scenarios and timelines.
There's also the newer and currently less developed AH Tropes Wiki, started by a small group of AH.com enthusiasts.
The Other Wiki: Wikipedia has a (not entirely undeserved) reputation on the forum for being subject to bias by nationalist administrators: running gags and Flanderisation focus on Poles and Armenians, but there are plenty from many other countries as well. All this material was used in the AH.com: The Series two-parter "Citation Needed".
There's also an increased awareness of TV Tropes on the forum as well. Though some see it as overflowing with Anime and Ho Yay.
Trope Decay: In the past few years, the overuse of the term Alien Space Bats to mean "anything that seems implausible or not very probable to this board member" had lead to the erosion of its original meaning. Many senior AH.commers (but newer ones as well) disliked this trend because it had started bordering on complete Natter. They had campaigned to bring the term and acronym back to its roots and stop its overuse as a derogatory shorthand. It seems to have worked, since the overuse/misuse has largely been reversed and had pretty much gradually vanished as a problem during the 2012-2013 season.