Centrif is an Ask.com-style search engine powered by users' bookmarks -- in other words, you ask the site a question and it returns the link that others think provides the best answer. The site is still in its very early days, but founder Steve Wilson has just introduced some new features that should make Centrif smarter and easier to use. Other companies are already using pieces of Centrif's approach. For example, you can already use Google and Ask.com but Wilson thinks that user recommendations will return much more useful results. Wikia Search and Mahalo, on the other hand, also offer human-created search results, but Centrif's approach is a little less ambitious -- unlike Wikia Search, it isn't trying to build a full-fledged Google competitor, and unlike Mahalo, it's only relying on users to create the bookmarked links, not full pages of information. For queries ranging from "how to translate Python to Ruby" to "how to learn Japanese" to "how to cook chicken," Certif returns a few fun, hopefully useful results, and the database is growing. (Wilson says it's too early to release any usage numbers.) Still, as you might expect from a site that was essentially created by one man with the help of a few contractors, there were serious limitations. Probably the biggest was the fact that your search keywords had to match perfectly, as TechCrunch's Jason Kincaid pointed out. Now, however, Wilson has introduced some "dynamic learning" technology, so that Centrif can learn from your searches. For example, when I searched for "Japanese language" this afternoon, there were no links that included "Japanese" and "language" as keywords, but Centrif let me jump to the results for "Japanese." Then I clicked on the best result, and Centrif "learned" that's a good result for "Japanese language," too. Over time, this should make Centrif searches more flexible, and less an exercise in keyword-guessing. The site also added some other useful features, including spelling correction and ability for users to leave notes with their bookmarks. Philadelphia-based Centrif is self-funded, and Wilson says he has no immediate plans to seek venture backing.