Start with the data.
Aircraft. Weather. Transport. Space. Sport. Air quality. Find a source, then work backwards to the thing you could build around it.
Live and historical aircraft data
REST API↗
WEATHEROpen-MeteoForecast and historical weather data
No-key options↗
SPACENASA Open APIsAstronomy, imagery and space datasets
API key↗
SPACEJPL Solar System DynamicsSmall-body and solar-system data
Public APIs↗
TRANSPORTTfL Unified APILines, arrivals, disruptions and transport data
Anonymous + registered↗
ENVIRONMENTOpenAQGlobal air-quality observations
API key↗
SPORTfootball-data.orgCompetitions, teams, matches and tables
API token↗
CIVICGOV.UK Bank HolidaysUK bank-holiday dates by nation
Public JSON↗