I just released Oplop 0.2, my initial attempt at an application for using account labels and a master password to generate unique passwords for all of my various accounts. The source distribution that I put up includes both a terminal and wxPython interface. You can use the Oplop.py script to launch the application, first trying wxPython and falling back on the terminal version. If you get the svn checkout there is a py2app version if you would like to try to generate an OS X application (creating a standalone version failed for me, but an aliased application works no problem). There is also a J2ME version written by a friend of mine.
Do note the release number if you do give it a whirl. I have been using the application for all of my password need for months without any issue, but I make no guarantees. Version 1.0 will most likely come out once I feel comfortable thinking that others have used it without issue as well.