There's some interesting disclosure in Microsoft's 2012 proxy statement, about how the company spends money to influence election campaigns and public policy.
That's not quite right. More precisely, the proxy disclosure is about how the company will not take advantage of the Supreme Court's Citizens United decision to influence elections with dollars that can't be traced back to Microsoft.
"Microsoft recognizes the increasing interest of U.S. public company shareholders in establishing greater transparency about corporate political contributions. Microsoft discloses its political contributions to support candidates and ballot measures as well as how certain of our trade association membership dues are used for political activities. As part of our commitment to transparency, after the U.S. Supreme Court’s decision in the Citizens United case in 2010, Microsoft amended its Principles Guiding Microsoft Participation in the Political Process in the United States to clarify that Microsoft will not make independent political expenditures or electioneering communications as are now permitted after the court’s decision. The policy is available at www.microsoft.com/politicalengagement."
When you follow the link, you get additional information about Microsoft's campaign contributions and lobbying efforts, including a chart which shows that lobbying expenditures at the state level have risen to almost match those at the federal level.