I'm currently a lurker in a local RPG organization that's trying to promote RPGs. I've been part of it for more than five years now and one of the biggest hurdles the group has been facing is the lack of new blood. Sure, there are the occasional new faces but for the most part, whenever I attend an event, it's more or less the same people running the show. Ever since the big fandom boom in the country (which I'll associate with the popping up of The New Worlds Alliance), we've been trying to get more gamers from these other fandoms. Interested in Star Wars? We'll run a Star Wars tabletop game (alas, where were you Saga Edition two years ago?). Lord of the Rings fan? Decipher's got you covered. Pirates of the Carribean? We'll work something out with 7th Sea (-cough- Pirates of the Spanish Main -cough-). Anyway, the hobby gaming industry I think is a spot missed by many SF&F fans. The most obvious ones of course are the RPG supplements.
For example, one thing Glen Cook's The Black Company series always lacked was a decent map. Green Ronin's The Black Company Campaign Setting not only contains maps of the world but includes a geography lesson of the setting and a brief summary of all the novels. Guardians of Order previously released a campaign setting on George R.R. Martin's A Song of Ice and Fire (the RPG license is now with Green Ronin) and it included not only artwork for the series but a history and timeline as well. During the recent cosplay competition at the Manila International Book Fair, one of the cosplayers dressed up as Ser Barrister Selmy. I didn't recall that he was dressed in such ornate armor but when the cosplayer showed me the source of his inspiration, it was from the Game of Thrones Collectible Card Game (CCG) from Fantasy Flight Games. The Wheel of Time RPG from Wizards of the Coast, while perhaps not as full of information as the two other RPG books mentioned, is nonetheless a good repository of Wheel of Time artwork and has an interesting bestiary and close-up maps of the city of Caemlyn and Illian to name a few.
It's not limited to just RPG books though. Various franchises have spawned numerous products that include board games, CCGs, video games, and comics. Not every writer gets a chance to publish a Silmarillion or The History of Middle-Earth but various material are released that expand and built upon the world. At the very least, works that are deceased (or on "hiatus" depending on your faith) such as Serenity might find new life in an RPG book or continued in a comic line which was the case with Buffy the Vampire Slayer. An example of an adaptation that made a big impact in its field was the video game Dune 2000, based on Frank Herbert's Dune. Dune 2000 was basically the inspiration for the ever-popular Warcraft franchise that came to dominate the RTS genre during the 90's. Peter Jackson's Lord of the Rings arguably changed the way how movies are made and was a big boon to New Zealand (well, Lord of the Rings and Power Rangers). It's all interesting to witness how a novel or franchise can branch out to other mediums and make a huge impact.