At a basic level, this document itself is a spatial hypertext. But it's hardly the first.
Spatial hypertext has a long history in academic research. Systems like
StorySpace,
VIKI/VKB, and
Tinderbox have been very helpful to hypertext researchers, academics, writers, and other people who need to organise things.
Spatial Hypertext is different from mindmaps. Mindmaps usually focus on just presenting information visually; they are diagrams more than information spaces. Spatial Hypertext, however, has always been intended to hold large amounts of information.
Research by Frank Marshall and Catherine Shipman (thanks for all the hard work!), have shown that spatial hypertext tools like VKB and Tinderbox are very useful for people who need to make informed decisions with little time and an abundance of time. I have used Tinderbox for several years to keep notes, organise my ideas, and even
create an interactive history exhibit.
Some literary works also use spatial hypertext to present an alternative to the paper book. Many literary hypertexts, such as
Patchwork Girl do this. I like
We Descend, by Bill Bly, which is a fiction made out of a collection of artifact documents. But I'm biased. This spatial hypertext publishing tool comes out of a collaboration with Bly to create a sequel to We Descend.