Tools
Small things that answer one question properly. They all run entirely in your browser, with no sign-up and no upload.
Which Side of the Plane?
For the northern lights, Mount Fuji, or just the shady seat. Put in your route and get the geometry instead of somebody else's rule of thumb.
TravelAstronomyFreePinewood Derby Weight Placement
Drag the weights, watch the centre of gravity move, then race your car against a stock one and read the gap at the finish line.
PhysicsCanvasFree
More on the way. If one of these is broken or wrong, tell me.