First, what is Type-Moon?:

Type-Moon is a Japanese video game company that is known for producing various games such as Tsukihime, Fate/stay night, andKara no Kyoukai. It was co-founded as a doujin (indie) developer by writer Nasu Kinoko and artist Takeuchi Takashi.

What are they doing now? Specifically, what is Nasu working on?:

TM's most current projects are Fate/EXTRA CCC, a sequel to the PSP RPG spin-off, and Mahoutsukai no Yoru, a visual novel. Nasu is the main scenario writer for each.

Outside of TM, Nasu has also recently become involved in Red Dragon, a novel writing project based on role-playing interactions between himself and other popular writers.

When is Mahoyo coming out?:

Mahoutsukai no Yoru, commonly shortened to Mahoyo, is the story of Aozaki Aoko as a high school student in the 1980s. It is all-ages, and has a release date set for April 12, 2012.

Leo: I would think of integrating the very basics just into the top of this page.  The best thing for the basics section would probably to have it organized series FAQs.  Nausverse being as diverse as it is, you can't get everything under one agenda.  So:

Fate/Stay Night:

Can Servants be harmed by normal weapons?:

You can find an all ages Let's Play here: http://fsn.seorinwastaken.com/archive/

What is Fate/Stay Night about?:

Fate/stay night tells the story of the Fifth Holy Grail War, a battle between seven magi and their Servants over an "omnipotent wish-granting machine". The seven Masters summon Servants, spirits of legendary or mythical heroes from human history, and fight until only the winner remains to use the Grail.

The story of F/SN revolves around a boy named Emiya Shirou who has been caught up in the war. He fights to end the conflict for good, and prevent any more death and suffering caused by the extreme violence of the battle. Other main characters are more iconic of the game, however, and usually more popular.

Why should I read Fate/Stay Night?:

Although Type-Moon got its start with Tsukihime while they were still independent developers, Fate was their first real project as a full-fledged video game company. Nasu's unique writing style and eclectic cast of characters remain to this day the primary source of TM's popularity.

Tsukihime

Can Tohno Shiki kill Servants?:

Short answer is no, not easily. 
His main obstacles are being able to perceive the death of powerful spiritual entities that the human Shiki has little understanding of, and then being able to attack such monstrous beings without instantly being killed.

Can Servants be harmed by normal weapons?:

No. Corporeal, physical phenomena cannot interact with spiritual phenomena.

Who is Arcueid?:

The titular character and heroine of Tsukihime.

You can find an all ages Let's Play here: http://lparchive.org/Tsukihime/

Kara no Kyoukai

You can find a translation of the light novel here: http://emptyboundaries.wordpress.com/

Angel Notes

DDD

The two categories are not exclusive: you could have a bunch of other questions in there.  Basically, we want the what's it about and why should I questions to be a pitch: this is where we try and make the reader want to try the game.  Also, important is links to the source.  We can't advocate downloading, but the next best thing is to link to the Fate and Tsuki LPs (Yes a lot of people don't like them, but they're easy to get to and easy to get in to), the Empty Boundaries KnK TL (Again, not liked by all, but the only complete English TL, and the one that's easier to read), the Notes TL, and what we have of DDD.