A must visit site for all the C/C++ programmers out there: SQLite.org
From their homepage:
SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine.
I just fired up Eclipse (with CDT plugins), copied one of the example C programs, and I could create database and run SQL queries against them in a jiffy. Agreed that running Ubuntu made getting the SQLite3 development libraries easy. But it should be almost as easy in getting the libraries installed from their downloads seciton.
The example program I compiled is just 26577 bytes (~ 26 kB) and I can pass along large subset of SQL commands to it along with the database filename. (Update: See SQLite - Amalgamated size for more information)
If you need a robust database for your application, but cannot opt for larger databases, SQLite is the answer. And best of all, it is in public domain - you are free to use if for any purpose.