Topic: sources for data feeds in xml or json

I would like to create an app which utilizes an existing data feed.

for example a grocery list app which has the aisle numbers that items are located in, etc.

Is there an existing directory of companies that make data available as a feed online in a format like xml or json? for example in the way that amazon has a feed for affiliates?

I have been googling terms like "json data feeds" but have not found much.

just wondering if anyone had run across any good resources.
thanks

Re: sources for data feeds in xml or json

By googling 'api json':
http://ipinfodb.com/ip_location_api_json.php (has both JSON and XML)
http://www.delicious.com/help/json (has JSON)
twitter also has JSON (e.g. https://dev.twitter.com/docs/api/1/get/ … _timeline)