Python is the best supported language, with bindings for almost every library available on maemo: GTK, Hildon, GStreamer, Bluetooth (bluez), SDL (pygame), Numeric and DBus.
PySnippet is a code snippet manager for any language. It features an user defined folder hierarchy, syntax highlighting, automatic clipboard copying and XML based data file.
PyGTKEditor is a text editor with a small screen footprint, fast syntax highlight for Python and PyGTK, fullscreen capable, regulars expressions search and many more other things specially designed for onboard developpers.