Brian Jordan and other readers sent in word that Google has taken the wraps off Knol, its expert-written challenger to Wikipedia. (We discussed Knol when it was announced last year.) Wired has an in-depth look. Knol's distinctions from Wikipedia are that authors are identified by their real names (and verified), and that they can share in ad revenue if they choose to. The service initially features a lot of medical articles, which is interesting considering that Medipedia also launched today. This medical wiki is backed by Harvard's and Stanford's medical schools.