It seems that the urlopen(url) methd of the urllib2 module 
leaves some undestroyable objects in memory.

Please try the following code:
==========================
if __name__ == '__main__':
  import urllib2
  a = urllib2.urlopen('http://www.google.com')
  del a # or a = None or del(a)
  
  # check memory on memory leaks
  import gc
  gc.set_debug(gc.DEBUG_SAVEALL)
  gc.collect()
  for it in gc.garbage:
    print it
==========================

In our code, we're using lots of urlopens in a loop and 
the number of unreachable objects grows beyond all 
limits :) We also tried a.close() but it didn't help.

You can also try the following:
==========================
def print_unreachable_len():
  # check memory on memory leaks
  import gc
  gc.set_debug(gc.DEBUG_SAVEALL)
  gc.collect()
  unreachableL = []
  for it in gc.garbage:
    unreachableL.append(it)
  return len(str(unreachableL))
  
if __name__ == '__main__':
  print "at the beginning", print_unreachable_len()

  import urllib2
  print "after import of urllib2", print_unreachable_len()

  a = urllib2.urlopen('http://www.google.com')
  print 'after urllib2.urlopen', print_unreachable_len()

  del a
  print 'after del', print_unreachable_len()
==========================

We're using WindowsXP with latest patches, Python 2.4
(ActivePython 2.4 Build 243 (ActiveState Corp.) based on
Python 2.4 (#60, Nov 30 2004, 09:34:21) [MSC v.1310 
32 bit (Intel)] on win32).