diff --git a/paramiko/client.py b/paramiko/client.py
index c13105e..ae25715 100644
--- a/paramiko/client.py
+++ b/paramiko/client.py
@@ -28,6 +28,7 @@ from paramiko.agent import Agent
 from paramiko.common import *
 from paramiko.dsskey import DSSKey
 from paramiko.hostkeys import HostKeys
+from paramiko.resource import ResourceManager
 from paramiko.rsakey import RSAKey
 from paramiko.ssh_exception import SSHException, BadHostKeyException
 from paramiko.transport import Transport
@@ -256,6 +257,7 @@ class SSHClient (object):
         if self._log_channel is not None:
             t.set_log_channel(self._log_channel)
         t.start_client()
+        ResourceManager.register(self, t)
         
         server_key = t.get_remote_server_key()
         keytype = server_key.get_name()
diff --git a/paramiko/resource.py b/paramiko/resource.py
new file mode 100644
index 0000000..135af15
--- /dev/null
+++ b/paramiko/resource.py
@@ -0,0 +1,72 @@
+# Copyright (C) 2003-2006 Robey Pointer <robey@lag.net>
+#
+# This file is part of paramiko.
+#
+# Paramiko is free software; you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+
+"""
+Resource manager.
+"""
+
+import weakref
+
+
+class ResourceManager (object):
+    """
+    A registry of objects and resources that should be closed when those
+    objects are deleted.
+    
+    This is meant to be a safer alternative to python's C{__del__} method,
+    which can cause reference cycles to never be collected.  Objects registered
+    with the ResourceManager can be collected but still free resources when
+    they die.
+    
+    Resources are registered using L{register}, and when an object is garbage
+    collected, each registered resource is closed by having its C{close()}
+    method called.  Multiple resources may be registered per object, but a
+    resource will only be closed once, even if multiple objects register it.
+    (The last object to register it wins.)
+    """
+    
+    def __init__(self):
+        self._table = {}
+        
+    def register(self, obj, resource):
+        """
+        Register a resource to be closed with an object is collected.
+        
+        When the given C{obj} is garbage-collected by the python interpreter,
+        the C{resource} will be closed by having its C{close()} method called.
+        Any exceptions are ignored.
+        
+        @param obj: the object to track
+        @type obj: object
+        @param resource: the resource to close when the object is collected
+        @type resource: object
+        """
+        def callback(ref):
+            try:
+                resource.close()
+            except:
+                pass
+            del self._table[id(resource)]
+
+        # keep the weakref in a table so it sticks around long enough to get
+        # its callback called. :)
+        self._table[id(resource)] = weakref.ref(obj, callback)
+
+
+# singleton
+ResourceManager = ResourceManager()
diff --git a/tests/test_client.py b/tests/test_client.py
index 32f1a30..a53ff0e 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -23,6 +23,8 @@ Some unit tests for SSHClient.
 import socket
 import threading
 import unittest
+import weakref
+
 import paramiko
 
 
@@ -59,7 +61,8 @@ class SSHClientTest (unittest.TestCase):
         thread.start()
 
     def tearDown(self):
-        self.tc.close()
+        if hasattr(self, 'tc'):
+            self.tc.close()
         self.ts.close()
         self.socks.close()
         self.sockl.close()
@@ -125,3 +128,26 @@ class SSHClientTest (unittest.TestCase):
         self.assertEquals(True, self.ts.is_authenticated())
         self.assertEquals(1, len(self.tc.get_host_keys()))
         self.assertEquals(public_host_key, self.tc.get_host_keys()[self.addr]['ssh-rsa'])
+
+    def test_3_cleanup(self):
+        """
+        verify that when an SSHClient is collected, its transport (and the
+        transport's packetizer) is closed.
+        """
+        host_key = paramiko.RSAKey.from_private_key_file('tests/test_rsa.key')
+        public_host_key = paramiko.RSAKey(data=str(host_key))
+        
+        self.tc = paramiko.SSHClient()
+        self.tc.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+        self.assertEquals(0, len(self.tc.get_host_keys()))
+        self.tc.connect(self.addr, self.port, username='slowdive', password='pygmalion')
+
+        self.event.wait(1.0)
+        self.assert_(self.event.isSet())
+        self.assert_(self.ts.is_active())
+        
+        p = weakref.ref(self.tc._transport.packetizer)
+        self.assert_(p() is not None)
+        del self.tc
+        self.assert_(p() is None)
+