It's not so much about what new stuff is brought to the table (although I know there will be plenty of new stuff since we're all discovering new stuff in the show all the time), but rather a collaborative effort to put together every conceivable piece of Dark Shadows information in one easy-to-navigate location.
Here are some examples of what would be there.
Episodes
You can go on to the site and find all kinds of information about a specific episode you've just watched. There'll be the original dates of taping and broadcast, a synopsis, notes on the timeline, any memorable quotes. There'll be a complete cast listing for the episode, including which episode each character and actor appeared in previous to that one and which one they next appeared in. Same thing for the crew, certain locations or sets, or important props or items. You'll be able to find out where the episode has been released on video or DVD. There'll be a complete list of bloopers people have found in the episode, or just any trivia or important notes of interest.
Movies, Novels and Comics
A similar format will be available for each and every movie, novel and comic book that's ever been published, including notes on how things differ from other sources.
Characters
Say you want to know everything there is to know about your favorite character, or a character you don't remember much about. There will be an article for every character to have appeared on Dark Shadows, major or minor. The article will detail every bit of known facts (including contraditions... where would DS be without a myriad of contraditions) about the person, complete with episode sources. There will also be a complete list of appearances (episodes, novels, comics, etc.) for that character and which actor(s) played him/her/it.
Actors/Crew
The actors and the crew will each have thier own page with a list of the characters they've played, in addition to as much biographical information as is known about them. There will also be links to official or fan pages, etc.
Locations & Other Items
Same as with characters, locations such as the Collinsport Inn or the Eagle Hill Cemetery will have a seperate article detailing all known information and important events that have occurred there and when.
Video and DVD
Each video and DVD release will have its own page, explaining when it was released and what content it provides.
Reference Books
KLS and Pomegranate Press have released tons of reference books for DS and its spinoffs. Each one will have its own page, explaining the content, availability, etc.
Timeline
There will be a page for each year. Under the year, it will document every important fact that occurred within the show, either on-screen or mentioned in passing. Also, real life things will be listed there, seperatly, for example, airings of shows, convention dates, actors' birth or death dates.
Plus much, much more... literally whatever anyone can imagine people would want to read about. This will cover all things Dark Shadows, including all three TV incarnations and all of the spin-off material. Keep in mind though that this is meant to encyclopedic, meaning that there won't be reviews or opinions on things. Speculations on things should only be mentioned as asides (and labeled as a specualtion) and only appear if we all feel it's important.