If your application can tolerate a day's delay then perhaps you should look into just grabbing the XML files from Yahoo! Finance. They let you download the history of any of their stocks and use in your own code.

For example: http://finance.yahoo.com/q/hp?s=AAPL&a=08&b=7&c=..., and click on the download Spreadsheet link at the bottom

updown.com, an investing startup that really likes advertising to me on Facebook, uses these guys

http://www.quotemedia.com/

They seem to offer live quotes, but I cannot personally vouch for their services.