Sending HTTP requests from App Engine

Yes. More details here: http://code.google.com/appengine/docs/python/urlfetch/overview.html

You can use the Python standard urllib, urllib2, or httplib libraries to make HTTP requests. When App Engine starts, these libraries make HTTP requests using the App Engine URL of the fetch service, which runs on Google's Scalable HTTP Request Framework.

Here's an example:

import urllib
from xml.dom import minidom
from google.appengine.api import urlfetch

params = urllib.urlencode({'p': loc_param, 'u': units,})
full_uri = '?'.join([url, params,])

result = urlfetch.fetch(full_uri)
if result.status_code == 200:
    return minidom.parseString(result.content)