Markets Data Center - Wall Street Journal has it all, on one page 

Market Summary - intraday industry indexes including international markets

Stocks, ETF & Futures Map - FinVis with 24/7 maps with charts and screener, and all market data 

Health of the Market - Short and intermediate-term outlook by a Forum member 

Great Charts

FreeStockCharts - REAL-TIME intra-day charts of everything 

S&P 500 Sharp Chart - with Bollinger Bands, ADX, and other indices updated by StockCharts.com in real time

S&P 500 ETF Gallery View - daily & weekly charts with continuous update from StockCharts.com

Sector Performance Chart - bar chart of eleven sectors over any time period (right click slider to pick period).

S&P Sector Carpet - performance of 500 stocks grouped by sector

Intermarket Performance Chart - relationship between stocks, bonds, commodities and the dollar 

U.S. Treasury Yield Curve - can be created for any point in time, and with links to yield charts

Technical Analysis

Chart School - Generally a great place to learn Technical Analysis, including definitions of indicators 

Sector Charts & Ranking - charts in all time frames (investigate site to find much value) 

Fundbuster - analysis of ETFs using various technical parameters with a portfolio owned by the analyst

Fundamental Analysis

Current Economic Data - News of the past and week ahead, and tables of GDP, etc. for most countries.

ETF Database - Information about all Exchange Traded Funds such as performance, portfolio, fees, and trading volume.

Stock Screener - Screen for industry, earnings, dividends and analyst recommendations. 

ETF Screener - Fidelity has fixed screens or make your own.

S&P NetAdvantage - JM Library (need card no.) gives company, industry, mutual fund data & ranking

Federal Reserve of St. Louis - Data & charts on the economy updated Thursdays

Dividend Paying Stocks - Find them with yield charts to see the trend, and general info with some good retirement calculators

Stock Lists and Calculators - Lists of all types of stocks in many industries.

Closed-End Funds - Ranking and content, and plots of CEF premium/discounts

Pundits

John Mauldin - Thoughts from the Frontline (subscribe to excellent free newsletter) 

Bill Gross - Bond market king is retiring.

Jim Cramer - Recap of his "Mad Money" show, and news from TheStreet.com

Andrew Tobias - "Money and Other Subjects"

John Hussman - Weekly comments on the market

Strategists of StockCharts.com- Articles on Goals, Style and Strategy for Investors

General Investment Websites

Kiplinger.com - Business forcasts, personal financial advice (including a forum), and many financial calculators 

Yahoo Finance - News and views with detailed information about every stock/ETF

Wall Street Journal - Stocks, bonds, currencies and more.

IRA Planning - Required minimum distributions defined and other IRA topics