wxWindows (Score 1)

I ported a Win32 MFC app which graphed a heartbeat line for a particular metric to wxPython http://wxpython.org/ recently and it's worked out great. It now works on Win32 (nicely wrapped up using py2exe and Nullsoft Installer) as well as any Linux system with the wxWindows libs installed. It was even easy to make a simple curses interface for the hard-core command liners. Our ops team has modifed the code now to measure and graph all kinds of metrics, all of which are multi-platform and don't require compilation via Visual Studio. Highly recommended.