Theres also an open source bitcoin price rss feed generator included in the bitcoin simple php tools .

code on :
 https://github.com/neofutur/bitcoin_simple_php_tools

discussion on :
https://bitcointalk.org/index.php?topic=68205.msg1164417#msg1164417

examples :
http://p.b.gw.gd/pricefeed/bitcoin_price_feed.php?format=short
http://p.b.gw.gd/pricefeed/bitcoin_price_feed.php?format=fullticker