Microsoft has taken the wraps off its Bing Fund, its angel fund and incubator program, detailing the effort on Thursday. The company said it will be inviting promising startups, based in the U.S., to work with the program for at least four months, on a rolling basis. The Bing Fund said it will also invite starts in the Seattle area to use its co-workspace in Bellevue, and provide funding via a convertible note, introduction to strategic investors, and connections to experts to help companies, in addition to giving access to APIs and certain technology assets developed by Microsoft Research. The Bing Fund said it is specifically looking at startups building online and mobile products, with working prototypes or (preferably) an application or site that is already live. Microsoft did not say how much it plans to invest in each of the firms in the program, or terms.