Metakit is a small, portable database library using a hybrid relational / hierarchical data model with a column-wise internal storage format. For C++, include a single header file and 125 kb DLL or statically link directly. Ideal for desktops, embedded systems, smartphones, and PDAs. Bindings for Python and Tcl. A very mature, stable code base.
PAGE is a drag-and-drop GUI generator for Python. It is aimed at building single Python modules which can display a relatively simple GUI constructed from the Tk and ttk widget sets using the Place Geometry Manager. The generated Python code can execute under Python versions 2.6 and 3.1.
Scid vs. PC is a powerful chess toolkit. It has extensive database and PGN file handling capabilities, and can be used to play chess on the internet (with FICS), against a computer chess opponent, or for chess grandmasters to prepare for tournament matches. Additionally, Scid vs. PC can run automated computer tournaments with chess engines playing against each other.