MC Hammer
MC Hammer

The rapper, whose stylings helped popularize hip-hop in the 1990s, found another calling as an entrepreneur and investor. Although his social media dance site DanceJam fizzled, "Hammer," as he's called in tech circles, has invested in companies like the rapidly growing mobile payments startup Square and Bump Technologies, the developer behind an app that lets users "bump" their smartphones and trade contract information. Up next? WireDoo, a search engine still in development that Hammer and his team hope will ultimately offer more comprehensive results than current offerings.

@FortuneMagazine - Last updated March 29 2012: 1:47 PM ET
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