Stock screeners allow you to select specific stocks based on various criteria that you supply.

Charting services allow users to look at charts showing the price (and other measures) of a stock or mutual fund over time. The data for the charts comes from the stock exchange where the issue is listed, and vendors buy the data stream and package it. There isn't any difference in the data that is displayed on two different charting services.

Stock Screeners

CNBC.com: Stock Screener 
Google Finance: Stock Screener 
Morningstar: Stock Screener 
MSN Money: Stock Screener 
Yahoo! Finance: Stock Screener 

Charting Services

Big Charts 
MSN Money Charts 
Stockcharts.com 
Yahoo! Finance Charts