In the last couple of weeks, there's been a little twittering about Osun.org, a search engine that seeks out documents of the PDF, .doc and .ppt persuasion. And that's all we know.
Well, we know that it's designed to mimic Google's front page in all but colour. But apart from that, things are murky: there is no "about" page; there are, in fact, no links on the search page at all that offer to take you to explanation.
A search in whois reveals that the domain name is owned by Wang Linhua, who gives Shanghai as the city of his (?) origin. We also learn from the same source that it's moved around a bit: among something like 13 different name servers over half a dozen years. A search on serversiders.com tells us that it's getting a lot of traffic — almost in the top 100 in the .org set of domains — most of it accelerating in December. And, too, we learn there that it's currently hosted on one of Google's servers, ranking high among sites hosted there. (Google hosts many non-Google sites on its servers.)
I suspect but have no basis for knowing that Osun.org does not index the web itself but relies on Google's efforts in some way. It is probably merely a version of a custom search engine, restricted to the three filetypes. I haven't tested this hypothesis really at all: I ran one test, searching for [canada OR canadian military filetype:pdf] on Google, and the corresponding search for PDFs on Osun.org; and I found that the results were almost identical for the first half dozen items or so, but then began to diverge after that. (I'm attaching the Osun.org and the Google results in two pdf files, if you'd like to have a look.)
Until Osun.org reveals more about itself, this is nothing but a curiosity for researchers. If you're desperate for something that you just can't pull to the surface in Google, you might consider using it — after all, web search results are like money: murky origins don't affect their utility.