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 management to boost performance. ValueAct leaders also often sit on the boards of the companies in its portfolio. Founded in 2000, ValueAct manages some $3.5 billion on behalf of institutional and wealthy individual investors. It has offices in Boston and San Francisco. ValueAct focuses on making investments in the software, pharmaceutical, media and communications, and medical technology sectors. The firm's current portfolio includes stakes in Thomson Reuters, MDS Inc., VeriSign, Misys, and Immucor.