When ValueAct Capital Partners sees untapped value, it acts. The firm, known for its activist slant, buys large stakes in undervalued companies and works with their management to boost performance. Founded in 2000, ValueAct manages some $1.5 billion on behalf of institutional and wealthy individual investors. ValueAct's current portfolio includes stakes in Advanced Medical Optics Inc. (contact lenses; nearly 15%). The company successfully thwarted Advanced Medical Optics' proposed acquisition of Bausch & Lomb in 2008, saying Advanced Medical could not successfully absorb its rival.