Yahoo!Finance - Charts (Ability to compare against indices, multiple moving averages, and multiple other stocks, as well as capability to use a variety of statistical and technical analysis tools)

Multex Investor  - Charts (Includes much of the same, but is more limited in number of stocks which can fit on one chart and has fewer technical analysis tools)

Quicken/Excite - Charts (No technical analysis tools, but can compare any number of stocks, and can automatically compare vs. competitors)