To develop Quick Look plugins, you can visit this site, which states:
QLPlugins.com is a repository for Quick Look Plugins, which are
available starting with Mac OS X 10.5. In addition, I seek to provide
information for developers seeking to create QuickLook Plugins and to
power users looking to use QuickLook more effectively. If you have
developed a QuickLook Plugin and would like for it to appear on this
website or are aware of any QuickLook Plugins I have missed, send an
e-mail to firstname.lastname@example.org and I will include it.
About QuickLook & QuickLook Plugins
QuickLook was introduced by Apple in starting with OS X 10.5
(Leopard). By selecting a file in the Finder and pressing the
space-bar, a preview of the file pops up. QuickLook Plugins, or
QuickLook Generators, are files ending in .qlgenerator and are used to
generate these previews. These plugins are also responsible for
generating the previews in CoverFlow mode in the Finder.
While many file formats are supported out of the box, some common and
many obscure formats are not. Fortunately, Apple's programmers made it
easy for developers to create their own custom QuickLook Plugins. This
site seeks to serve as a repository linking to these Plugins and as a
resource for developers looking for information on developing their
own QuickLook Plugins.
The Quick Look developer page was also linked in this Apple discussion forum post.