A good example of a practical, useful database app, I know politics lists every Federal politician, with their office and parliamentary contact details, email, website, Twitter link and so on, plus their positions, party and history. There is a photo of each politician and details of parliamentary sitting dates. Search can by name, party, state, positions or other variables.
The main users of I know politics have been people who work within Parliament House and need to keep track of and recognise its nearly 200 politicians.