I'm starting a new project, a wiki search engine. It uses MediaWiki, Semantic MediaWiki and other minor extensions, and some tricky templates and bots.
I remember Wikia Search and how it failed. It had the mini-article thingy for the introduction, and then a lot of links compiled by a crawler. Also something similar to a social network.
My project idea (which still needs a cool name) is different. Althought it uses an introduction and images copied from Wikipedia, and some links from the "External links" sections, it is only a start. The purpose is that community adds, removes and orders the results for each term, and creates redirects for similar terms to avoid duplicates.
Why this? I think that Google PageRank isn't enough. It is frequently abused by farmlinks, SEOs and other people trying to put their websites above.
Search "Shakira" in Google for example. You see 1) Official site, 2) Wikipedia 3) Twitter 4) Facebook, then some videos, some news, some images, Myspace. It wastes 3 or more results in obvious nice sites (WP, TW, FB). The wiki search engine puts these sites in the top, and an introduction and related terms, leaving all the space below to not so obvious but interesting websites. Also, if you search for "semantic queries" like "right-wing newspapers" in Google, you won't find real newspapers but "people and sites discussing about ring-wing newspapers". Or latex and LaTeX being shown in the same results pages. These issues can be resolved with disambiguation result pages.
How we choose which results are above or below? The rules are not fully designed yet, but we can put official sites in the first place, then .gov or .edu domains which are important ones, and later unofficial websites, blogs, giving priority to local language, etc. And reaching consensus.
We can control aggresive spam with spam blacklists, semi-protect or protect highly visible pages, and use bots or tools to check changes.
It obviously has a CC BY-SA license and results can be exported. I think that this approach is the opposite to Google today.
For weird queries like "Albert Einstein birthplace" we can redirect to the most obvious results page (in this case Albert Einstein) using a hand-made redirect or by software (some little change in MediaWiki).
You can check a pretty alpha version here http://www.todogratix.es (only Spanish by now sorry) which I'm feeding with some bots.
I think that it is an interesting experiment. I'm open to your questions and feedback.