Websites:

Washington Department of Financial Institutions
Features downloadable booklets (.pdf) with the basics on investing in stocks and bonds, including various ways to evaluate the performance of each.

Morningstar Investment Research Center
The "Investing Classroom" portion of the Help & Education section covers stocks and funds separately, with sections that address performance evaluation (for instance, course 107 in the stocks section is titled "Introduction to Financial Statements" and covers how different financial statements can be used to determine a company’s health and performance). Financial information on stocks and funds are available, along with analyst reports, by searching for a particular company or mutual fund.

MSN Money
Guided research for stocks and funds; stock quotes by company name or symbol; various articles on how to begin investing in the learning center.

TRL Databases:

Business & Company Resource Center
Investment reports, financials, and rankings available for individual companies.

Books:

Investing for Dummies by Eric Tyson 
332.6 TYSON 2006
Section on returns; information on yields, research, statements; chapters on print and electronic resources used for research.

Getting Started in Financial Information by Daniel Moreau
332.6 MOREAU 2000
Chapter 6, "How Performance is Measured." Covers yield, return, tracking performance, using research.

Wall Street Journal Guide to Understanding Money and Investing by Kenneth M. Morris
332.632 Morris 2004
Various sections on how to obtain, parse, and use available information to evaluate stocks, funds, and bonds. Good graphics and examples.