I have held on to this bit of code I picked up along the way but have not used it for anything yet. It will retrieve stock quotes from yahoo and display the info, with some tweaking you should be able to add an interface for this.
<?php
$fd = fopen ("http://quote.yahoo.com/d/quotes.csv?s=AAPL&f=sl1d1t1c1ohgv&e=.csv", "r");
$contents = fread ($fd, 200);
fclose ($fd);
$contents = str_replace ("\"", "", $contents);
$contents = explode (",", $contents);
echo "<p>Apple stock tracker</p><p>Most recent trade: <b>\$$contents[1]</b></p><p>Today's Change: $contents[4]</p><p>(Prices delayed up to 20 minutes.)</p>";
?>
EDIT: It will display this.
Apple stock tracker
Most recent trade: $127.43
Today’s Change: +5.21
(Prices delayed up to 20 minutes.)
