Standard & Poor's Compustat, available through WRDS through the JMU Libraries. This source has annual and quarterly data for companies for at least twenty years, but in some cases much longer than that. Available in downloadable spreadsheets in various forms, including spreadsheets and SAS.
Mergent Online, available through the JMU Libraries. This source has fifteen years of financial data for public (and some private) companies around the world. Available in downloadable spreadsheets.
Reuters. This source has three to four years of financial statements for publicly-traded companies around the world.
Stock price data
University of Chicago's Center for Research in Security Prices (CRSP), available through WRDS through the JMU libraries. This source has daily and monthly stock prices for all NYSE, AMSE and Nasdaq traded securities; monthly prices since 1928, daily prices since 1975. The data can be downloaded in to Excel or SAS.
Yahoo! Finance. The Basic Chart has a link to historical prices that you can download in to a spreadsheet program.