A business site that appeals to non-traditional readers: Hot concept, not so easy to pull off. See Mainstreet.com, the pop-money spinoff from TheStreet (NSDQ: TSCM) still trying to figure out what it wants to be. And there’s FiLife, the DJ-IAC (NSDQ: IACI) JV, which, despite a long time in the oven, isn’t close to fully baked. Monday, Slate launches The Big Money (will go live sometime early in the morning), a business-oriented spinoff in the works since last year. With so many above-the-fold business stories all going down at once (Lehman Brothers, Bank of America-Merrill Lynch, AIG restructuring), they’ve either picked the best or worst of all possible launch dates (I’m leaning towards best). I had a brief chat with a time-pinched James Ledbetter—in addition to all the normal, last-minute headaches, the site is scrapping the feature it had in the works for two months, in favor of a big one on Lehman. On the timing, said Ledbetter: “If I were in perfect control of events would I want to be making enormous changes the night before the launch? Probably not… (but) This underscores the fact that this is an extremely critical time.” It’s Ledbetter’s belief—or hope—that this critical period augers well for a business media site with Slate’s “authority and tone”. In terms of the pace, again, you can look to Slate (owned by the Washington Post (NYSE: WPO) Co.). It won’t be the first with breaking news, but it plans to react quickly to relevant stories. On Monday, besides its main story on Lehman, watch for various sidebars and followups as events develop. From the content I’ve been able to check out so far, The Big Money is clearly the most fully formed and self-assured of the new business sites. It’s got the requisite blogs, including one exclusively focused on Google (NSDQ: GOOG) (joining the club). Another one is YouTube BrandWatch ("measuring how companies are viewed online"), which should be very familiar to Slate readers. Besides stories directly about business, expect wry coverage of the business press itself. As a little sampler, the staff has been twittering for several weeks at Twitter.com/WSJquips—slight pokes at Journal stories, one line at a time. In addition to the articles themselves, the site is also experimenting with various online tools, like a socially responsible stock screener and a chart builder to insert into PowerPoint presentations. Of course, web tools on financial sites standard, but here the opportunity is to imbue them with an editorial voice, potentially blending apps and journalism in interesting ways. In terms of The Big Money’s own money, the site is launching with two sponsors: American Express and Infiniti. Both companies have prior relationships with Slate, but the ads being run on the site aren’t just Slate ads—rather they’re direct sponsorships of the new launch.