9. Harmonix takes off
In 2005, Harmonix, the Cambridge company founded by a pair of MIT-trained geeks, released a little videogame called Guitar Hero. You know the rest. MTV promptly acquired Harmonix for a cool $175 million; in 2007 came Rock Band. The company continued to grow (until layoffs just a few weeks ago) and made huge headlines this year with the release of The Beatles: Rock Band (pictured). Expect a Green Day game in 2010.