Stocks can go up or down based on major movements in related markets. These sites track other major markets that can (or will) have a major impact on today's stock market (and possibly your high-level investing pursuits):
PensionTsunami: Pensions are massively underfunded across the corporate and government world; this site gives you all the news and analysis on this critical topic.
Economic Collapse Blog: Michael Snyder's site provides thorough research on major financial and economic issues that could be problematic for the U.S. economy.
The Bubble Bubble: This site follows all of the potential bubbles that could burst in the next few years.
The Korelin Economics Report: This site provides news, commentary, and interviews with analysts on precious metals, stocks, and related topics.
Dollar Collapse: John Rubino's site tracks the U.S. dollar, currencies, and related markets.